Textures again

I have recently lowered my attempts to texture a highly detailed mesh, but I still have problems with a lot of the models. I was going to convert all textures into .png files, and was wondering if that is better to use than .jpg files. I have a "Stop Sign" that I've been working on, but I can't seem to get the textures to stick to it. I did have to "Duplicate" the "Sign" mesh because it would not let me place 2 textures on the part. I used 2 texture channels, I made sure the channels were assigned to the proper meshes, and I UV mapped them as required, but still no textures. I can send the model to anyone who can help me fix this problem. Let me know if you would like to see the file. Thanks for any help.