I'm not familiar with the Snipping tool thing, but I generally set the image size to 800x600 pixels. That gives small image sizes at typical screen/monitor resolutions and fit easily on most desktop monitor displays without needing to scroll.
If you store the images on something like photobucket, then it's possible to post the link to your album image for sharing to the forum, which gets around the file size limitation.
What OS are you running, XP, W7, etc and we'll see if we can help further.
Brian
ps - apart from the obvious storage issues with large photos, they also take longer to download, especially if there are several in a long topic. I'd presume the limit is partially there to improve server response and folks don't have to wait whilst a page downloads?