These are all wallpaper samples; I recognize some that are definitely from Ferm Living. I think they are about $3-5 each, and look at how great they look hanging together! The identical frames bring them together.
You can get the look of this collection by cutting pages from an architecture book. Browse used book stores for tomes about Palladio or the architecture of ancient Greece.
Wall decals are a wonderful way to dress up any room. I've seen everything from dinosaurs to botanicals available lately. They are easy to remove and you can experiment with different compositions when you to switch things up.
When you use your own photographs with identical frames and mats in a grid, you can include all kinds of subject matter.
Vintage shell-tanicals are easy to find on eBay and if you're lucky, you'll come across an entire book of plates. These are perfect for the coastal look. You can also use illustrations of plants, beetles, foxes - whatever you like.
A series of prints from one artist always makes for a great collection.
Working on a next-to-nothing budget for a family homeless shelter, this designer turned a bunch of very inexpensive pieces into a collection by arranging them like a pro.
You can pick up a variety of mirrors at discount stores and make a fun wall out of them.
If you want to cover the entire wall like this, pretty much anything goes. The only thing that is uniform is the general spacing between each frame.
Try a wall of brightly colored kid art. Use frames - no masking tape or push pins allowed! (By the way, this is NOT to meant to debase this artist's work; it was the bright colors that made me think of the exuberant artwork of children!)
With the slightest bit of computer font saavy and a printer, you can be the artist and mix in some favorite sayings or words into your arrangement.
Mrs. Limestone has turned her every day supplies into art!