Welcome Rod, photos are easy. There are two basic approaches
Posting photos as attachment seems to allow the most people to view them.
http://allmetalshaping.com/showthread.php?t=115
Or you can host them in the built in gallery (or elsewhere on the internet)
http://allmetalshaping.com/showthread.php?t=159
This approach can result in lost photos if you host them off site and your photobucket (etc) account goes away.
600 DPI is a good size. VERY large photos won't load and really slow down folks opening the post. Some members are still on dial up connections.