As of the October 29th update, Wikia will be storing its images in a new location. While it updates, you may notice that uploading has been disabled for a short period of time. The time for this period is not known.
"Later this week, Wikia will begin transferring images to a new file storage system. This will be done on a wiki-by-wiki basis, with the smaller, older wikis getting updated first. When the script is transferring the images on your wiki, uploads on your wiki will be disabled. This process will be done quietly on the backend and there will be no major disruption to your wiki other than the disabled uploading. Uploads will be disabled for a small period of time, usually less than an hour."
Just a short message in case you're active during this period of disablement and wonder why you can't upload images.