I would probably work from the inside out. Meaning, figure out how to border the panel (and probably do the same for the outside borders). Then you can figure out what to place in the space between the borders. Once you have highlighted the panel and 'seperated' it, a pattern may pop into your head. The idea of stars almost always works with a patriotic panel. The best thing when you get a brain block (I find) is to step away from it. I have some wine, watch a movie and relax - clear the head. Then things start flooding back in!