[Help] How to get comic style textures

I have a little personal project that im working on, of a city im building in 3D, I want to make it in the same style of the games: borderlands, walking dead. Another example is the cartoon art the band gorillaz has. I want to go for the same style with the city textures. Having failed at searching for a database for these textures online, I thought about just searching for regular city textures and modify them in photoshop… I’ve been playing with the poster edges, native photoshop filter, but the result is bad, it doesnt look like a drawn picture at all and anyone who will look at it will spot it right away and tell that the texture was done with poster edges filter. Can anyone give me some pointers on how to get this done accurately?
Im attaching an example picture, original tiles from walking dead game:

http://img26.imageshack.us/img26/2130/tilervinteriortiles.jpg

thanks in advance

a tablet and some patience?

You might find using sharpen filters help give the visual effect due to harder edges.