1. Progressively more complex edge spots.
2. The 100 and 500 are too similar. I would change the base color or have drastically different edge spots.
3. Sleepy's Basement at the top, Denom at the bottom, lose the martinis and make sleepy larger to show the detail better.
3.a Sleepy's Basement at the top, lose the martinis, denom smaller and on sides (100/C-note, 5/Five Spot etc.) and make sleepy larger to show the detail better.
4. That graphic lends itself well to a hot stamp.