Remove some avatars

Replace them with others from O2

@emanuele45 pointed out that some of the avatars were those of other projects.  Even though they are in the O2 set and all are OS projects, it still may be best to drop those and replace with something.

This drops the obvious ones, others that were part of the distro or are very generic so those seem fine, but I added in a couple of extra just in case.

For some of the existing ones, I opened the svg files, scaled to the size we need, and re-saved, that's why you see some of them again (maybe slightly larger (less white space) and higher res .. all were run though a png crush as well.