The avatar file size requirement is a bit too small. It's not easy to get a 65x75 file down to 10KB. 15KB wouldn't be too hard.
A quick test shows that a 256-color 65x75 Windows BMP (a straight bitmap, not compressed in any way) is only 6178 bytes, so you ought to be able to make a JPEG file at least that small.
In reply to:
In Photoshop you can size the image to a 65x75 JPEG with a quality of 0 out of 10 and still not be below the 10KB file size.
Most standards-conforming JPEG implementations offer finer control of the image quality (often a 1-100 scale). Most of them also offer some other options for the JPEG encoding that can reduce the file size. You might try GIMP, which is freely available for Linux, Mac OS X, and legacy operating systems.
If the picture originally came out of a digital camera (still or video) or a recent scanner, make sure you are _not_ saving the EXIF data with the image. This is a header that has the date, time, exposure length, f-stop, etc from the camera - not too many bytes but every one helps. The EXIF header often also contains a small thumbnail of the whole image - it's only maybe 5 kb, which is no problem compared to the 400 kb - 800 kb JPEG coming out of the camera, but is bad when you're trying to reduce the JPEG to 10 kb.