I post my images on Photobucket generally at about 1.5 MB and provide the direct link to this site. Don't know if that is causing a problem. If so respond (or PM me) and I will provide smaller files.
Happy to help.
When I am editing files, I generally save two versions. One will be at the maximum size, say the cameras full capture size at 300 dpi density. That is the master. I will then save a version at 800 x 600 or smaller at 72 dpi that will be used for the web. If you were to save a version at 800 x 600 at 300dpi and view both side by side on a video screen, you will not see any difference, but the file sizes will be incredibly different.
CORRECTION - Gekko reminded me that it is not DPI, but only the file size and the "quality" setting when using lossy formats like Jpeg that will affect file size, my apologies.
By way of example, most of my recent diatom photos from the Armand Bayou are around 800x600, 72dpi at 90 quality and less than 100k in size. If there is any deficiency in the presentation, it stems from my abilities in capture, but not the file size.
If you upload these to the forum storage, the reduced file size will usually mean that the cost of running the site is reduced, as most hosting contracts charge for data and or storage. The site will run and load faster because you can load ten small files in the time it takes to load one large file. As long as the presented image is the same, it makes good sense.
Again, I have no issue with posting large files, just suggest it be done in a way that doesn't make the decision to download the large file for an unsuspecting user, but instead seeks permission by way of clicking on a link.