I think it's great that you're exploring your own design capabilities. good for you! it's fun AND a great way to "make" quilts when you're low on fabric. who knows? maybe you'll end up selling patterns to others. :P
if you're really serious about it, you should go online and "shop" around among the many free drawing programs out there. paint is very limiting. here's a free program. i've only played in it a little, but i think it might work very well for you once you get the hang of its many features.
http://www.inkscape.org/
you might also want to check out the Open Office suite. it has all the same type programs Microsoft Office has but is completely free.
http://www.openoffice.org/