Thanks everybody for your kind replies. The funny thing is - I have never seen a life gekko. On TV and photos, yes, but in real life I only know lizards (small ones) and chamaeleons (at the zoo). But I was always fascinated by those little critters.
inkskin - I ususally buy FIMO on eBay (and you never know how old that stuff is that you get there) and it is always ok. But - in contrast to super sculpey - FIMO (the regular one, not the soft one) is always hard and crumbly at first and needs to be warmed and kneaded extensively. I've read that some people even use a foord processor to speed this! I ususally twist and knead the stuff between 20 and 30 minutes before working on it - but then it's fine. It's quite boring and feels like hell when you want to be creative and have to do such tedious preliminary works.
Imagination is intelligence having fun!