We had to re-create American money (two different dollar bills), using any kind of American iconography. I went with Aliens and their  where they were allegedly spotted.

Its a fun premise. It looks more like board game money than actual cash, but that could be an avenue to expand on. Also more bills and coins with different aliens/ cryptids on it would be cool too.

More sci-fi looking fonts. Illustrations done in the same style would help them look more uniform (spooky looking linocuts/woodblock prints maybe).  More bills and coins too. Also If I end up going the board game route, designing a board, box and instructions would be fun.