Yes, you will get an improvement. But for image manipulation, I think a normal harddisk will do fine. Most of the manupulation are done in the RAM, so getting more RAM will definitely help.
People use striping mainly for video recording where they cannot afford dropped frames due to harddisk being unable to sustain writing at the required data rate for a long period of time. Burst rates are usually quite fast but once the buffer fills up and the harddisk cannot catch up, this is where the video will just stream pass as dropped frames.