well i can tell u now, ur gonna need some hardcore software to do this, but a simple google search can get u those.
for starters, ur gonna need rco editor, to create rco's.
and ur gonna need microsoft paint or a similar program and convert the pic to .bmp format, and rename to 01-12. it must be a certain resolution also, i think 480x272, but i may be mistaken.
ur icons that u wanna make must be 55 or so pixels tall each. 50 pixels for the picture, 5 more for the border to get cut off. cluster all those to gether into an rco and name it topmenu_plugin.rco
ive never made one before, please somebody else help, i was just saying what i have read other places. wait for a second opinion.
in addition to what mcman posted... for your 01-12.bmp your gonna need a 01-12 image merger to merge the 12 images together. And they have to be named 01.bmp 02.bmp 03.bmp and so on...once its thrown into the 01-12 image merger it will create a single image titled 01-12.bmp.
But yeah those tutorials should keep you busy for a while, if you need help on anything just post back here or in one of the forums on the site mentioned above.