when I save my chart to local file, while in esignal, it has a option that allows me to adjust the size of my chart before I save it to snapshots or whatever file I put them in on the computer. Adjusting the size of the chart that way may or may not have anything to do with the forum accepting it as the file you download in here has to be small in terms of kilobytes...something like 300 or less. That's small.
If your charts have too many Kb's, about the only way I know to reduce that is send the file to "MS Paint" and reduce it there. A pain in the ass, relatively speaking.
Hope that helps...maybe