Softbrick after flashing theme - how to restore without losing sd content

Hi,
so I tried to install a new theme and during the install the phone froze. I tried to access the recovery again, but I can't, the phone stucks at galaxy s3 screen. However I can access download mode.
My question is, what do I have to do to keep my SD Card content (like pictures)? Which firmware should I flash? I was on Wanam Lite Rom.

Thanks for Help
Matt