DIY bookshelves and wall decals.

Bookshelves

I love the bridge bookshelf, and now I've found the DIY for it !
This is so simple but also it breaks up the normality of a bookshelf.
See how to make one here

Skateboards are often a beautiful substitute for shelves, skateboards often have beautiful graffiti on them and the sandpaper on top of them can keep books from slipping if you tilt the shelves like this, but here the wheels have been used to support the books in some places.

This one may be a bit pricey, you probably don't have many tables lying around that you have no use for, but if you got 2-3 it might work because you saw the tables in half and paint them the same color or different colors to add a bit of artistic flair to it.

Wall decals.

This one is from the same website, I love this idea because it gives you complete control on what you want to do, it's just contact paper cut down and glued on, you can read more here.
And it can a simple form like bricks or if you're handy and patient, something like this;

And you can always find pictures online and with a little photoshop skill, make an outlines of that image that you can print out and draw on the contact paper.

And if you have no such talent, then I recommend you check out Etsy.com, and search for wall decals(you have already did that if you press the link above), there are thousands of different wall stickers in all sizes and price ranges, you can definitely find something you like there.
Here are some of my favorites;