Extension Manager

Edit the alias list
Adds autocomplete to search & tagging.
Turns BBCode into HTML
Displays brief updates about whatever you want on every page.
Allows admins to modify & set custom <head> content
Allow users to favorite images
Add HTML to some space (News, Ads, etc)
Handle JPEG, PNG, GIF, WEBP, etc files
Handle FLV, MP4, OGV and WEBM video files.
Ban IP addresses
Show various forms of link to each image, for copy & paste
Annotate images
Allow users to make comments on images
Show a list of uploaded posts
Allow users to rate images "safe", "questionable" or "explicit"
Allow users to score images
Tracks & displays how many times a post is viewed
Allow users to send messages to eachother
Shows a QR Code for downloading a post to cell phones
Allows displaying a page with random posts
Do things with a random post
Show a random line of text in the subheader space
Regenerate a thumbnail image
Allows people to replace files for existing posts
Show various bits of system information
Let tags be split into 'categories', like Danbooru's tagging
Allow images to have tags assigned to them
Keep a record of tag changes, and allows you to revert changes.
Recount / Rename / Etc
Provides "Trash" or "Recycle Bin"-type functionality, storing deleted images for later recovery
Shimmie updater! (Requires admin panel extension & transload engine (cURL/fopen/Wget))
Allow users to write a bit about themselves
Sitemap with caching & advanced priorities