That happened to me when I was trying to come up with a new card for the untitled .sig card expansion set, which jackalwere used a delta symbol for the set icon. (No problem there, and I wouldn't ask him to change 100+ cards.)
And then I realized that what I wanted the card to do didn't really mean anything. And then I realized that this hasn't stopped anyone (including me) before.
Two cards come to mind:
First, the Leftovers card, pictured here:
Second -- okay -- there isn't a second. I just went looking for it, and I couldn't find it. I thought it was in philbarfly's Seven Seas expansion, but it isn't. Basically, I remember recently seeing a Terrain card that canceled Rivers and Lakes bonuses. Maybe it was a Spell card, which wouldn't be bad. Maybe I misread it. I hope so.
Anyway, my new "sig" card, even if isn't technically a "sig" will be around soon enough, as soon as I figure out what it should do. It's a new Terrain card, and it's meant to fit the theme of the expansion. And yes, there is a theme to the expansion. I think.