Sorry normally I'd try to offer more help with this type of question but I'm currently not at home and I don't have my Kindle with me to test anything out.
However, if you pop over to the link to my website below, you'll find an article on gmail with several different ways of logging in (didn't test pictures sorry) and maybe one of these might be better for you.
Note that I cannot guarantee they will work if you're not on the 3.0.3 update:
http://www.kinworm.com/2010/10/gmail...-kindle-3.html