Never use it tbh.
Tried once... and occasionally i'd find something and think "hell yeah!" only to find it was 800px wide.
I mean the idea is good, but as to whether it's useful, it's only as good as the quality of what people upload. Sometimes an 800px image would be fine for paint reference, or a kit design, so we can't say ban small images, but a way to filter them based on resolution, a bit like google images.
Other filtration options:
Backgrounds:
->Indoor
- - >Studio
- - >Other
->Outdoor
- - >Press Image
- - >Race Track
- - >Atmosphere
- - >Other
Styles:
->Stance/hellaflush/VIP etc.
->Track
- - >DTM
- - >Touring Cars
- - >Time attack
->Rice
->Concepts
->JDM
etc, etc, etc
Another potential idea that may be helpful was discussed probably 3 or 4 years ago back on DM. Some sort of bodykit finder. You match angles by moving some dots and lines on your base image (this would be done for uploaded images), then the database will be scanned for close matches...
Maybe some sort of donor moderators would be helpful too? To keep the section tidy and check tags etc on new uploads.
Final idea - "rate this donor". Similar to the chop rating system, and it could maybe count towards the user's points too... it might encourage better quality of uploads.