I know this is an old subject, but since an older post dealing with this has been locked, here's one more VERY easy way to get your image sizes down to MOC-legal dimensions.
http://www.imageoptimizer.net has a user-friendly interface for re-sizing one image at a time. Check the lower left of their home page. You set maximum dimensions, upload the image, and download the re-sized image.
You can also download a (free) program that will optimize a group of images at one time. You put all your big images in one folder and select the folder to optimize; every image in the folder is re-sized with a couple of clicks. It's a very cool way to re-size a camera full of vacation photos before uploading to your trip journal. The only "cost" is a small tag at the lower right corner of the re-sized image with Image Optimizer's URL (practically too small to read).