If you don't intend to expand it to something more than
Decoded's Custom Cursor maybe you could work on that project adding a few more graphics as available options?
Author has stated that he's in the process of creating a tutorial on how to make custom cursors,
so I'm guessing he would be responsive to requests about that or general info.
Edit: To add some relevant info.
Most cursor changing packages are not addons, they're graphic replacement packs.
That means they're not meant to go into
<wow root folder>\Interface\AddOns\
but instead to
<wow root folder>\Interface\Cursor\
Before the usual questions, graphics elements that are not meant to be overridden
in this way are ignored by the game when it loads but cursors are among those elements that are ok.
(at the time of posting)
API access to the cursor is provided through
SetCursor and
ResetCursor.
This however will not change the standard cursor
(when your mouse is hovering the WorldFrame)
Cursors in-game are context sensitive (change depending on what's under them).
In any case a combination of graphic replacement (for the standard cursor) and addon (for other cursors: attack/gather/loot/quest or whatever) would probably
get you quite far into customizing Cursor appearance throughout the game.