I uploaded several smiley images which were .gif and they went in no problem, however these were "animated" .gif and when I placed them on my pages they just showed the first image of the animation.

So the answer to the question seems to be "Yes" you can upload .gif at least...

I've only been using Magix Website maker for a week and am very well pleased with the results - still a newbie though.  Good Luck.