Holy spam on this post.

Lets look at what you have going for you - white fixtures and pale, semi-neutral walls.

Kitchen:
- Since the tiles are a pale blue - why not use that as a jumping point and incorporate a lot of bold accessories in deep teal and turquoise? I'm talking about glasses, bowls, serving pieces, towels, soap dispenser. Mix and match but keep it all in the bold blue family. Add some brown and natural materials like wood salad bowls.
- If mold is a concern, you might want to incorporate outdoor fabric to make a roman shade, or use a bamboo shade which is a little hardier.
- Add an outdoor rug/mat underfoot.
- Add a couple of framed prints to the walls. You can hand a fancy hook above the tile and use a nice rope or ribbon to hang the prints lower. Get cheap white matted frames at IKEA.
- That vent thingy - what is that? Is it necessary? Are there screws that you can undo and store that thing under your bed or in a basement or something?
- Hang a mobile or plant to the right of the window - try to disguise that thing on the wall.

Bathroom:
- Definitely get a shower curtain - make it white and bleach it now and then. Or buy it cheap and replace occasionally if there are mold issues.
- Get an outdoor rug.
- Does the tile go up to the ceiling?

I think the kitchen is adorable! I'd hardly change a thing.

Do however, replace the cheap plastic towel holder and re-think that white table.

As the person above said, embrace the blue tile with blue accessories. Add neutrals such as wood, etc.

Um, maybe get a stove at some point? To go in that big empty space?

I can't make too many alterations at my apartment, either (alright, I'm just too lazy to commit to painting it back), so I decorated simply.

In the kitchen, I used stick-on command hooks to hang a few pretty dishtowels at varying heights; I also got a bright rug in a similar color scheme. I think the advice to stick with teal/blue is good, and you could mix in yellow/gold etc for flavor. Maybe curtains above that window and a few objects that you're fond of (a special bowl, a vase of flowers, etc) on the counter for personality. I set out a pair of interesting mugs on top of my microwave and it made a big difference.

For the bathroom, same advice: Set the color tone with the shower curtain, which takes up so much room that you can really change the bathroom with it. Maybe something simple and classic, given the amount of pattern on those tiles. Fluffy, indulgent rug; artful stack o' towels; a command hook here or there-- you're in business!

Good luck!

chrome in the accents. chrome wastebasket for bathroom. chrome storage shelves. not really sure what style you want, but chrome will give u a modern look and still fit in nicely.

I don't know how universal ikea products are, but they have panels you can put up to cover tiles you don't like. Here's the US link:
http://www.ikea.com/us/en/catalog/categories/departments/kitchen/19121/

I have seen people use a sort of sticky vinyl paper over their existing tile. I can't remember what it is called but it comes in a roll and you can get it at any home improvement store. It goes on well and can be peeled off without leaving any residue behind. It comes in a bunch of different patterns. I even know people who cut pieces and put them on their cabinets because they were brown and they wanted them white.

In the kitchen, maybe you should skirt the table on the right and use the same pattern with a shade for the window? That would at least add color that could be a jumping off point for you!

Well, as a tenant, there's not much you can do about the tile in either room, so might as well embrace it. Clean the heck out of it, especially the grout. The back of the kitchen counter, the bathtub and the other fixtures could probably do with a good re-caulking. It may seem trivial, but a nice bead of white instead of the dirty, crumb and mold collecting line that it is now does wonders for the overall look.

That vent hood is actually pretty cool. Clean it up, inside and out, and see if you can polish the metal bits! I have no idea what that thing is within it... It looks plumbed...is that a water heater? try to paint or obscure the pipes below it to draw less attention to it.

I agree completely with the poster that suggested some bolder blue colors for the kitchen, and if you're allowed to paint, I would give the kitchen walls/ceiling above the tile the same bold color that's being incorporated elsewhere. Also, if you're allowed to paint, then maybe those cabinets want to be white instead of the brown that competes with the flooring. (and that little patch of tile to the side of the stove is just weird)

If you want to go further, I'd find some nice light fixtures to replace the florescents, if you can and they're not just task lights. Wiring a replacement fixture is easier than it sounds, gives a nicer less harsh light, and is generally an improvement that landlords are happy to keep. Good Luck!

You can't paintm you can't renovate and you'll be there for only 3-4 years? Doesn't give you alot of options, does it?

How about making the most of what you have by simply emphasizing the blue & white with more blue & white and wooden objects, keeping it clean and going out and enjoying everything Barcelona has to offer?

Last thing I'd do in Barcelona is concern myself with how the kitchen looked - I'd be out enjoying the scene and spending all my money going out and seeing Spain!

Another vote for bold blue in the kitchen, and I'd add in some orange to make it a little brighter.

I agree with Ban Clothing on the sticky-vinyl-tile-coverup. Even if you just do the far wall, that will make a huge difference in how you perceive the room when you walk in. You could also hang some string globe lights around the ceiling to make it feel more cheerful — that could also be an alternative to using the harsh fluorescent light.

For the bathroom...maybe use black accessories? Shower curtain, rugs, toothbrush holder, etc. It would be simple but sleek.

Mi consejo: cierra los ojos.
My advice: close your eyes.

Wow, I lived in a crappy apartment in Sant Andreu for 4 years there, and I gotta say, compared to you I was lucky!
First off, clean the hell out of that grout - yuck! If by the time you cleaned all you can, it is still gross, replace it. Just the grout won't be a problem with the landlord, and it will make a huge difference (walls and floor).
I second amy's suggestion of bold appliances and accessories.
Paint the wall/ceiling on the kitchen, something complementary, or maybe bright white to bring out the white in the tile. Also, maybe switch light plates, to bright white. You can always save the original ones and put them back in place when you leave. And get rid of that towel holder, it makes the kitchen look even more greased.
Maybe a good scrubbing on that hood?
For the bathroom, I really don't know. Maybe a colorful chandelier, with the colors picked up by the curtain/accessories/linen?
Just consider this: with BCN apartments, you are in luck to have such a huge kitchen (ours fit one person only!)