What you need to do tereith is first go to
http://cgcookie.com/blender/2011/06/16/creating-a-lowpoly-concrete-barrier-part-02/
Watch the tut, it explains UV mapping.
Lets say you want to apply textures to a cube. You want each face of the cube to have a different texture. But as you said the entity maker only allows you to use one texture. As you will see in the video, that uv mapping lays the 3d object flat called unwrapping. this is you UV map, Now you apply which textures you want on each face. You need a third party tool to do this like Paint.net,gimp,photshop. When you have all your textures placed. You make a single texture with all the textures then apply it like a quilt to your cube.
Also your going to want to try and work with TGA and DDS files with FPSC.
Blender is funny, youcan fumble around with it and not quite understand it. But one day you'll see something or do something and it will start to make sense. The above tut did it for me.
One more thing you can find great free textures @
[href]cgtextures.com[/href]
