when you say not acceptable... what do you mean ?
do you get an error message ?
I find .GIF or .JPG work the best
I use gif files for circuit drawings, they are usually less than 10 kb often less than 5kb
for actual photos of gear use jpg and do some compression, get then down to below 100kb and preferably below 60kb, that makes them quicker to upload, and also for people viewing them in a thread. and as i said in the first post get them down to q smaller physical size 640 x 480 is excellent.
I kept returning to Picassa and dropping the size which automatically drops the kb. The size is now below 2kb.
I then went through the routine of installing it and the pic appeared in the screen in the right place but when I tick the box to save changes an error message comes up saying 'upload failed'.
The pic is still there in my page but obviously not in the forum.