Custom Textures?

[MrHooker]

So a couple newb texture questions. Can I have my own custom textures? Can I re-skin freeport with high rez textures and make it look cool? Or does everyone's texture files have to match and I'll get an error or something? If you are allowed to does each texture have a size limit say 600 x 800 or can I load my own bigger ones?

Thank you.