1. So for future reference I should skip making "clones" for pong and Mario type games since they are virtually unusable?
2. Also, are there unrestricted 2D or 3D sources for artwork that I can use so I can put my material in a portfolio upon completion?
1. What new and interesting programming problems can you solve in a pong clone? You can make side-scrolling jumping games for your portfolio, but they should have something new and interesting about them.
2. Check the Visual Arts forum. I'm sure this question has been asked and answered many times there.