Start with Red Dodo. .
http://reddodo.com/
Choose a template and put in your chosen text.
Then save that animated GIF file to your computer.
Then go to Free Online Image Editor.
http://www.online-image-editor.com/
Find that saved animated GIF file and upload it.
Then go to EDIT>Crop and adjust as required.
It's very easy to use.
Here I am cropping an image to a square 110x110 pixels.
I then save this new animated GIF back to my computer.
I now have my required avatar, at the right size.
Nifty, easy and all free.
Thanks to Red Dodo and Free Online Image Editor.
Cheers. Si
Links checked 14 June 2012