Hi,
I fixed a bug in the image upload page: when the checkbox "Automatic resize/recompress picture if needed" was checked, sometimes the image was re-compressed even if it was not needed (i.e. if it was already small enough).
If you notice errors or strange behaviour following that, do not hesitate to report it.

Tomorrow or in the next days, I'll publish another update already implemented in the test site, where thumbnails are loaded differently, to reduce the load of the server.
The caching of images and thumbnails should also be better handled by the browser.