Thanks to you both!
I tried postimage.org to see how it would work, and it's exactly what I wanted - free - and I didn't see any references to 'packages' or payment plans or anything.
IIRC I selected '17-inch monitor' size when uploading, and then it sizes based on that wherever you paste the link. The links are not intuitive, though, I didn't find one that was a 1-step link-paste into here, had to copy one and then put it inside the 'img /img' stuff. A mild hassle, but not the end of the world.
For continuity's sake, here's a link to the next thread on the next trailer:
http://www.rctruckandconstruction.co...ad.php?t=13137