Short version: Images are showing now, Firefox is running, and I'm happy. Thanks for the help! =)

Long version:
I took comp's suggestion and exported my bookmarks, then googled on how to remove my user profile on Vista. Unfortunately, the page that I referred to said that I needed to delete the profile folders and thus I only deleted two folders in the Local and Roaming folders of my AppData.

After trying to start up Firefox, I got an pop-up error message stating "Firefox is already running, but is not responding. To open a new window, you must first close the existing Firefox process, or restart your system," so I restarted my system but ran into the same problem. Confused, I uninstalled and reinstalled Firefox (downloading the 5meg installation file took an hour...) before restarting again.

So I finally did what I should have done to start with, which was google the damn error message -_- and I found out that I needed to delete the profiles.ini file as well since I had nuked my only user profile and didn't copy it / make a backup. That wrapped up the problem and I'm a happy camper now.

For reference:
Instructions on how to uninstall Firefox and remove a user profile
This page does not mention the profiles.ini file, so beware.
Fixing the error message