There is a file size limit. Here are the specs:

Here are the various technical specifications for the forums.

FOR FORUM ATTACHEMENTS

    * Max of 4 images per post

    * 125Kb each but a total of 250Kb for all for combined

    * Max width and /or height of 800px

    * .jpg, .gif & .doc are OK

OFF SITE IMAGES

    * Inline images are OK - photobucket etc....

    * I have found that 700px wide is great to avoid horizontal scrolling.