The ones that sell for more than a penny.

Like these two I have in the market place currently
http://steamcommunity.com/market/listings/753/302010-The%20Hangar
http://steamcommunity.com/market/listings/753/280500-The%20Sewers

I love these:

Gone Home: http://cdn.akamai.steamstatic.com/steamcommunity/public/images/items/232430/585645162577d307192505011b2a179b990f8e37.jpg
Ibb and Obb:
http://cdn.akamai.steamstatic.com/steamcommunity/public/images/items/95400/d34b52db76042ca69e9c41e1b5f7b0d2815c8c51.jpg
Spirits:
http://cdn.akamai.steamstatic.com/steamcommunity/public/images/items/210170/b3ccf0c4675b864cea6901b46fcfa40a5a9a98fd.jpg

I love the Rust bg :3

Shovelware Queens, just look it up ;)

Anything from The Whispered World, although this one is my favorite.

http://steamcommunity.com/market/listings/753/113200-Wrath%20of%20the%20Lamb
http://steamcommunity.com/market/listings/753/231310-Eclipse%20(Profile%20Background)
http://steamcommunity.com/market/listings/753/238210-Confrontation%20(Profile%20Background)
http://steamcommunity.com/market/listings/753/221040-Lepotitsa
http://steamcommunity.com/market/listings/753/297410-Deep%20Space

I love this one ;)
http://steamcommunity.com/market/listings/753/245130-Rocklands

looks like this in my profile : http://puu.sh/fxzbH/19f8d45f80.jpg

Arconia and Dosc
Market Link
How it looks on a profile

http://steam.tools/backgrounds/#/

good for discovering new ones.

you can sort by price, and by supply and demand view all the "good" ones on top

I like mine. :P It's not too flashy, not too complicated, not too colourful.
(I've been wanting to add a few more animations to the middle frame, but procrastination wins! So this will do for now.)

http://cdn.akamai.steamstatic.com/steamcommunity/public/images/items/283680/6a7b0599269bcacf6df071478e1eb6fe4321a4a9.jpg
Astebreed

I like the one I'm using

try mine, steamcommunity.com/id/iml3042

art + calm

My favorite so far
Alliance Domain / Aeon Command | Full View
Love space and starry backgrounds.

The Void / Aeon Command | Full View
Blue vs Red / Aeon Command | Full View
Cyborg Domain / Aeon Command | Full View
Eclipse / Solar Flux | Full View
Lossageus / Sol Survivor | Full View
Nebulae / Space Rangers HD: A War Apart | Full View
Hyperion / Solar Flux | Full View
Kerbin / Kerbal Space Program | Full View
Space 1 / Defy Gravity | Full View

Cute ones:
Merry Go Round / Sugar Cube: Bittersweet Factory | Full View
Boogin Baddys / Monsters Ate My Birthday Cake | Full View
Blue Skies / Tower of Guns | Full View
School of Squirts / Bastion | Full View
Animal Orbs / Castle Crashers | Full View

i like theese ones as a fan of history and also as a guy:
http://cdn.akamai.steamstatic.com/steamcommunity/public/images/items/55230/4fb8f0acc41d69a14612867d854b2434a5ebab78.jpg
http://cdn.akamai.steamstatic.com/steamcommunity/public/images/items/214950/87ad20741f0813e5f642bebc6baa0a2fcb2071d6.jpg
http://cdn.akamai.steamstatic.com/steamcommunity/public/images/items/34030/7f160661d159be2121228c72b2d9be6c41698726.jpg

You're ALL invited to our wedding
http://cdn.akamai.steamstatic.com/steamcommunity/public/images/items/257970/aaf86d2f5b9d01b80af7ef5970b40e4b7aef8865.jpg

I really like mine... Its a large picture of Red from Transistor

http://steam.tools/backgrounds/#/transistor

Shamala
Steam store

Shamala & Millia
Steam Store

Didi and her imaginary friend
Steam Store for Christmas is very good.

Lucifer
Steam Store

Gumiho the Nine Tailed Fox
Steam Store

[]() []()

i like mine, it's very blue

aquila banner!

I like the pinball arcade backgrounds http://steamtradingcards.wikia.com/wiki/Pinball_Arcade

Edit: I'll trade someone a game for Twilight Zone bg.

Cthulhu Saves the World - Dark Beach
Race the Sun - Energy

Space (Civilization V): http://cdn.akamai.steamstatic.com/steamcommunity/public/images/items/8930/7edb27dbfffc7a8c646f1b46bfe2464f86b49931.jpg

Store: http://steamcommunity.com/market/listings/753/8930-Space?filter=civilization%20V

http://steamcommunity.com/market/listings/753/299890-On%20the%20Ice?filter=Hockey%20Manager

Pretty sure you won't find a better one in here ;)