For a long time, when people would ask what size image to post in forum threads, I would advise a 1024px max. Now with displays reaching higher resolution, I've been advising a 1600px max, though I wonder if 1300px is a better compromise. Our forum software automatically resizes large images to fit the browser window, but this doesn't change the file size. Ie, if we had a 2400px limit, the images would still fit, but those on a slow connection will have larger files to download. The other issue is that our server port bandwidth is limited to 1Gbps, which means that if enough folks are browsing simulataneously and the images are large, overall site performance will slow for everyone. Currently our attachment system automatically resizes images larger than 1600px to 1600px. It does not resize externally-hosted (eg, Flickr, Zenfolio, Smugmug) proxied images, but that's something I'm looking into. We have members embedding full res images at times, and a thread page can literally jump into the 100s of MBs when this happens. In terms of guidelines, what do you think we should ask? 1600px? 1300px? 1024px? Again, whatever limit we choose as a guideline, I eventually hope to implement via software so that externally hosted images will automatically be resized.