Not sure what motivates you to tie a new fly, but as I cruise the intertubes, I see many great patterns that just need to be tied. One came across my screen today called the Razor Foam Caddis from Hatches by James Spicer of Colorado Skies Outfitters.
Simple, clean and designed to float high without a lot of floatant, this is a cool way to use foam--wrapped as the body.
Probably will catch some trout and certainly pan fish.
Keep it simple.