that would probably be better as an app, rather than a hosted service.

I run picsur. It’s not an image resizer like that. It’s like Imgur, but self-hosted and can take size arguments as part of the query. I use it to host images for a markdown based blog and keep the sizes under control.

On a side note, I recently started noticing so many sites that use full sized images regardless of the actual size it shows up on screen.