Message Icons can be added just by uploading new files to your noncgi/icons directory, while keeping the filename structure intact (ie. if the last file in there is icon14.gif, you should upload icon15.gif, then icon16.gif, and so on).
Instant Graemlins can be added by a hack if you have 6.0X - look for the Smilie Mod topic in our 6.0x Mods forum. If you have 6.1.0, this is a standard feature.
---Skorpion