It's not SWC Team members, and it's not possible now. It's from the old rules/way of hosting images, where you were permitted to have your SWC avatar link to an offsite hosting of the image. Syn and others use an image rotating script or something like that to rotate their images on their hosted server.
It's still possible to rotate your signature that way, since the Signature is a user-editable html-enabled field.
You'll also notice some people with GIF's as their Avatars, which is also a grandfathering of old rules that are no longer possible.
Similarly, some characters have a single name, which again, is old rules where you were permitted to only have 1 name. It's not possible now.
“Although technically you could arrest an ASim they can simply access you account and unarrest themselves anyway, so it isn't an issue. But they generally hang around on their Acclamators anyway. ”
I know that's somewhat true, but I don't believe it goes that far. According to the rules, even a level 0 could A/E a 7.5 with a really lucky RNG roll. I know it would be hostile to your health, but so is floundering around the galaxy making pennies. I'm not the one to be doing it, but, given an infinite amount of chances and no repercussions, isn't it so that a new player could arrest a vet?
Usually it ends up having to be slab bombed - where you build slabs to cover the planet, then build up enough population to control it and let the remaining slabs decay. However if you are wanting to own it personally, you will have to build shield generators, or give it all population buildings to a faction for safekeeping. Players technically can't own planets unless they are 100% shielded.