You can easily get rid of that Madcow with the levels option in Photoshop, healing/stamp tool/ and exposure options.
As for the sites, they are all really excellent, but if you really want custom content to be personal and match the theme you want, you cant rely on others or other pictures for it once you get the swing of custom content. Its really not that hard to create textures from complete scratch in Photoshop. Its all about filters, layers, opacity, magicwand, bevel and emboss,..............well there is alot of steps, but you really can create some cool stuff with it.
Im actually working on a video tutorial split into 3 about creating a face using polygon extrusion, UV mapping it VERY fast and effective with UBER awsome techniques Ive figured out, Creating the skin from scratch in Photoshop, applying it to the model, and exporting it all into source! And you get to hear my Uber awsome voice too
lol
Ill post it in the forums, and if a moderator wants to offically submit it, then