Yes. I have a lighted leather cover and also have a Gelaskin on mine - been using it for ages with no problems at all. Infact I would thoroughly recommend getting a Gelaskin and an official cover - they look fantastic together.
If you use some of the cheaper 3rd party cases though (i.e. not an official Amazon one), the colour may come off the case and go onto your Gelaskin. You don't get this problem with the official Amazon case though.
Before I had an official Kindle case, I used a Tesco Kindle Premium Leather case, and the black colour ended up coming off the case after a while and ruined my Gelaskin.