Two full sheets sewn together to make a new slip cover for the whole futon? It'd be relatively simple sewing. I've made covers for a couple of pieces of simple IKEA furniture and it's pretty straightforward. If you don't have a sewing machine, but a friend does buying all the materials and taking them out to dinner would probably work in your favor. :)

Maybe a big colorful throw or duvet cover would work. Draped over and tucked in with some snazzy cushions?

Can you remove the current cover and dye it? If so, the material must be natural fibers or you'll get a tye dye affect.

If you go with MeeCee's idea, you can purchased these iron on tapes that you can use instead of sewing. Just place the tape between the 2 sheets, iron and they are 'sewn' together

Good luck.

I think some pillows and a throw would be great, but you might prefer something more dramatic. Mabye this ikea hack for stenciling slipcovers: http://www.ikeahackers.net/2011/06/customize-your-henriksdal-slipcovers.html

Ikea slipcovers are actually perfect for fabric painting.

Here is an example
http://itsgreattobehome.net/2011/04/11/tutorial-customizing-your-ikea-slipcovers/

If you have some DIY skills, hand painting the fabric could be really fun. Practice your painting on a old sheet, and try to pick 2-3 colors that are close to each other. Olive, Kelly and Spring Green, for example - or a Dark, Medium and Light blue. Or you could do an Ombre hand dying effect.

If you're worried about stains, white actually might be a good move - I know tons of people that swear by whiote slipcovers since they can be bleached. Any color or effect will not be able to be bleached and so will be much harder to get rid of, and I'd be worried that dye or paint would not wash well if you really need to tackle a stain.

If you want color, I'd probably just go with some fun pillows and a throw blanket, or making my own slipcover out of sheets (since the lines of the couch would mean very simple sewing).

If you don't dye it, use some scotchguard or other fabric protector and get some pillows to add some color. I'm not crazy about dying fabric, especially if you've never done it before.

id paint something beautiful in the middle and added few bright pillows on both sides

I've dyed Ikea slipcovers before. I bought dye from the local art store (slightly better than RIT dye) and used the washing machine. As long as your slipcover is wet all over, the dye should take evenly. I always use vinegar to set the color. If it turns out funny or you don't like the color, use the RIT dye remover to remove the dye. It is simple, but be prepared to wash out/wipe out the inside of your washer afterwards.

I don't get this post. How do we make suggestions about what to cover a couch with when we can't see the rest of the room? And if you didn't want to spend money on something other than Ikea, I doubt you're going to be keen to hear that you need to go to a furniture upholstery place and have a slip cover made as that will cost you a few hundred dollars-more than you paid for the furniture. So guess it's a DIY or dye. There are people that professionally dye things-check with your dry cleaner if it's a good one. But again, that will probably cost you more money than you want to spend. There are a lot of solutions, most of those solutions cost either more time or money than the piece originally cost. It's Ikea. They used to use East German slave labor and now they use Chinese slave labor. You can't compete. You're going to put more into it than you paid for it to get a tailored look, settle for a slightly sloppy DIY look, or settle for what you have.

If you want a plain colour and you're not confident dyeing something so large yourself - and you would need a big, non-communal, washing machine to dye something as big as that - you will find that some dry cleaners still offer dyeing as a service. Look for ones who advertise curtain alterations and wedding dress preservation etc

Everyone is thinking way too hard about this... just get a fitted sheet - buy 5 in different colours - and lay it out like a bed slip the fitted sheet over it and put it back as a couch. Easy. You can cycle them through, wash and replace super quick. You can even vacuum it for a quick clean when you're doing the floors.

Stamp or stencil it w/flexible fabric paint. You don't even have to do a repeating pattern and it will look great.

I wonder if you could fold it back and forth (like a paper fan), then bind sections with something like duct tape before immersing in a tub of dye, for a sort of ombre-ikat pattern when the tapes are removed?

There are places that make custom covers for IKEA sofas that are not too expensive - one of them is http://www.comfort-works.com/

I have a similar futon from Ikea. I had some difficulty getting the slipcover on and off it so I just bought a couple light bedspead/tapestries from Urban Outfitters. They're inexpensive (usually just under $40) and can be used as blankets during the summer at the beach, at an outdoor concert, etc.

I've just purchased replacement slipcovers for my Ekescog (now Hovas) sofas from IKEA. I've had the white for 5+ years and simply bleach them. I wanted white for that reason, you can't bleach a pattern. The reason I've bought new ones is mine have just worn out with pets and people. I purchased 4 slipcovers so I can keep 2 white and I'll be dying 2 of them a medium gray when they arrive. If you can wait, I'll let you know how they turn out. I wrote to Rit for suggestions and they said to prewash and keep the slipcover damp/wet for the dye process. Because of the size of the slipcover I will need at least 2 packages for each cover and another 2 for all 4 cushion covers. My greatest concern is making sure I have equal and enough water in the washing machine for each batch. I am hoping for the best and ready to accept sufficient. Stay tuned.

Either keep a supply of hydrogen perioxide/bleach, or get some RIT dye and change the color.

I think twocupsofjoe (the author) was referring to Comfort Works and not custom-works :p