Here's some suggestions..
If your using picnick, it's one of the WORST programs for a graphic maker.
Do exact dimensions like 400 x 200, 500 x 200, etc. So you don't end up stretching the page.
Download brushes, textures, and some PNGS to add some detail and coloring into your graphics.
If you ever think of adding fonts to it, please download some, for some variety.
Hope this helps.