Is that Alf on the screen?
Yep, that's him alright.

Great help in order to narrow down the game's year of release.
Supposedly the game was available for the PC & Amiga, but
I've never ever seen any other version than the Commodore 64 one - not even in screenshots...
edit: Sorry, didn't see your answer there Gribbler. Dude, are you reading my mind?!

'Zombi' was my first choice, but then I went with this one instead, since Zombi is a bit plain
colorwise...
All of you are on the right track. The game's not zombie exclusive though...