Go to Advance (on top menu) - Game Inteface
There you can change Icons (Like Gold, Lumber, Attack type Icon (like for magic you can make Firebolt icon)) Images, mostly not so important , Music, Sounds, Path and TEXTS. In Texts you can change like (Gold is given by killing creeps and heroes) etc.
You can also change color of texts if you know how xD
You just have to find it. Use T to get to texts easy, or I to get to Icons or Images