all you have to do is making a google+ account. there are already threads on here how to make usernames with a space - make such a youtube channel. then go to your google+ and click on the thing where you can share messages and stuff, you find it at the top right of the page. there is a camera symbol on which you have to click. then upload and share your .gif file. click on edit icon and choose the file you just uploaded + click save. then you have to log out and in again. it will not move on google+, but it will move on youtube. when you finish uploading, you see 4 squares surrounding your pic: you need to stretch them all to fill the pic.
only works with .gif-files that are 80x80 or 100x100 pixels. also uploading that icon only works in google chrome or safari i think, just like creating the name with the space.
EDIT: the icon from the channel where i did it first got removed, i guess it was too porn-ish, someone reported it ^^ but to see that it works uploading animated icons in 2012 you can also check this channel on youtube i did it there too: user/TCweed420