Can you provide more pics of the space? a floor plan with window and door locations? Your one pic does not provide enough information.

If you take the rug out of the room, you may find that the space is easier to plan. I think because of it's size and it's bold color, that it is holding you up.

Rugs on top of a carpet is not my favorite thing - the rug tends to get wrinkled and corners tend to flip.

I think the rug is a great place to start. I'd pick out another warmer color to contrast, maybe a orange or yellow, and add some great framed prints with some of these colors over your sofa as well as a few throw pillows in those color families with different textures/patterns.
Then just maybe a plant and one or two colorful accents (pretty colored glass bowls or a funky graphic figurine) on the coffee or side tables and it will start coming together. Good luck and have fun with it!

I would go with a really nice bright patterned rug with lots of bold colours.You can then pull the colour from the rug to be replicated in accents, pillows, etc.

Maybe you post the question too soon. Come back in a couple of weeks when the sofa arrives and gives more pictures of the room and gather your thought on what you are willing to do and your budget on it.

The blue rug is throwing me..but yes, some brights as orange or yellow will really look great with your grey and charcoal...then perhaps a little touch of an electric or jewel blue in the art! But still not the blue rug...check out rugs while you wait for your couch..something with a modern look to it..with the aforementioned color bits in it...I see that gorgeous yellow with a touch of chartreuse to it..in the pillows : ) I can see it's going to look gorgeous in there!

what do you plan to use the room for? tv? music? computer? a link to the sofa on a website would be fine. just give us a bit more to go on,

Get rid of the rug and chair. Keep the table, lamps, tray and use those as your inspiration for the space. It doesn't hurt to ask if you can paint, if not AT has some posts on removable wallpaper - I think. Enter the term in the search box or just Google. With that color carpet you can either stay neutral (creams, whites, grays) or go with pops of color.

Without seeing much of the room, that's all the advice I can give.

I think there are currently some disparate elements. Once the couch arrives, I would get rid of the recliner if it doesn't work with the space (if possible). The zebra-striped coffee table top or tray I think should go also. Artwork on the wall will help. Painting may also help, so see if you can do it! My design eye is not the best, so take my comments with a grain of salt.

a floor plan w/ dimensions, a pic of the sofa w/ dimensions (in the room or not), and a piece of art that you like (the art does not have to be for this room) really would help us help you

The rug is throwing me off too. Without the rug, since the space is so neutral you could go a couple of ways. You could get bright colored pillows and art, or you could get a variety of textured neutrals to keep the room chill but add some texture. Good luck!

Whatever else you do, that dark blue rug will be way too dark with all that dark grey furniture, I really think it has to go. Anything else is impossible to say without a floorplan - AT, can you please insist that these kinds of questions provide a floorplan?

Oh, but I for one love that zebra-striped tray, please keep that!

What if you mounted the blue rug on the wall?

Loose the rug. I would suggest checking IKEA for accent pieces in bold grey, orange, red and blue. I just found some great accent pieces there for not a lot of cash. Bold art on the walls and you will love the space. No painting required. you won't need to after all the bold accents.

I too don't like the rug. It's heavy and dark and weighs down the room. I'd find a throw pillow in colors and a style you like (try world market, pier 1, or etsy for some interesting finds) and then pull colors from that to add accents. The lamp looks a little cheap and generic. And I'm sure you could find a way to light the room and add style at the same time. Ikea has inexpensive lamps that are different styles--floor lantern types, metal, table lamps, etc. You could also search craigslist for something to catch your eye and even spray pain the base and find a new lampshade.

I also vote for getting rid of the rug- it's tying you down to a specific color palette and makes the room very dark. You may want to bring some bright colors into the room (either several shades of one color, or look at a color wheel and choose different colors that compliment each other). In a rental where you can't paint the walls, take advantage of other ways to add color- throw pillows, curtains, lamp shades, and framed prints. You can always go to a craft store and buy several single pieces of scrapbook paper in different patterns for under $2 apiece, and then frame them to make simple yet bright and bold statements on the walls.

I would also recommend adding plants into the room- somehow even just a few leafy greens can really make a room feel alive, relaxing, and comfortable.

Pick a bold fabric pattern for the lampshade. Plenty of DIY information on covering it.

Put some big silk flowers in the vase, ones that are a couple feet tall.

Paint the table?

I think the only thing you may need to change out is the rug. The blue is too close in color value to the gray recliner, and when you get your new sofa, you may find you need some pops of color.

Go slow. Don't go out and buy things now based on what people are telling you. Wait until you get the new sofa. When it comes, start working with colors you think will look good with it. Pull scarves, sweaters, dresses, etc from your closet and see what looks good with the gray of the sofa. You may not need an area rug. A big, bold piece of art that you can pull colors from may do the trick.

You might also try some patterned draperies if you have windows. Chevron stripes and geometrics, as well as contemporary damask patterns, are very in right now.

Please don't put silk flowers in that big vase! Go for some tall twigs, like twisted willow. Hobby Lobby has a whole bunch of different kinds. It will give you height and texture for your room. If you have a green thumb, add a couple of plants here and there for some living things in the room.

I like the idea of framing craft paper that someone else suggested. I am doing the same thing myself in my bedroom. I have new bedding, and the old floral framed prints do not go well with it. So I am changing them out using sheets of craft paper. Good idea for a cheap DIY art project.

Take your time in adding pieces to the room. It will all come together, and you will have a nice, charming room to enjoy.