could you add a image size limit or a image width/heigth limit, that resizes big pictures with gd, therefore it's not possible to upload pictures bigger then a special size
like every image get resized, if it's bigger than 1024x1024 or 130KB

I agree. As of right now, I am resizing them with a batch processor before uploading. Although maybe this seems like the job for an uploading tool, rather than the gallery itself (I know other galleries do this, but why use your webhost's CPU when you can use your own).

yeah, i resize my images, but i'm using my gallery as a multi-user gallery for a friend, she went to australia and she got a digital camera. she never used one before. And a PC isn't that interesting for her, she know how to use word and a browser like the most people

and the webhost cpu doesn't matter for me, just the webspace ^^