This is on the AO3? I'd upload them to a free image hosting service like Photobucket, then use html to include them: < img src="(the url)" > or if you want to be fancier < img src="(the url)" alt="(short description)" width="(the width you want it to display at)" >

Photobucket automatically generates html which will work but includes a link back them, you might want to strip out that link if you use a similar username and want to preserve anonymity. People will still be able to see the url if they make the effort, though.