GD support is broken in EZP 3.*
I've created some pathes to get it working again, check out the contribution: Living with safemode. You will still see some minor warnings (missing memento) with these patches, but it works. Don't forget to make the approriate .ini changes and if you have a choice: use imagemagick because GD cannot handle gif. (Everybody loves patents)
BTW. I've recently created a new patch that leaves .gif files intact and let gd properly scale images. I'll include this patch very soon in the 'living with safemode' contribution.