Most of the online resources for Sir Gawain are student essays and webpages. There isn’t a lot of good info on this poem on the web; you are much better going to the library and looking for books or articles.
The one good web resource is Luminarium’s Gawain Page.
I thought I’d give you the illustrations from the manuscript here:
When you have finished your essay, why not amuse yourself with some awesome Gawain Paper Dolls!
