Well done - click on Additional Options when you are making a post.
Allowed file types: doc, gif, jpg, mpg, pdf, png, txt, zip
Current Restrictions: 4 per post, maximum total size 4096KB, maximum individual size 1024KB. I can change this is it seems appropriate.
Note that if you attach a photo it will be resized to fit the page, but anyone can click and take a copy of the original, so only upload large photos if you are happy to take the risk that anyone can copy it.
If you limit your picture sizes to about 512 pixels on the longest edge, then it will be a good size to view on the screen, but not really of good enough quality for anyone else to copy and print.