read
this thread (especially the first post), and download any one of the mods in the first post. this will be your template for creating your own mod. you will update the graphic files included in this template to your liking, you do not have to touch the XML file.
open the file (it's just a zip) and drill down to /systemui/res/drawable-xhdpi/
you'll see a set of PNG files with the status bar icons shown in the first post. you will want to edit these PNG files to your liking or replace them with equivalent sized PNGs of your own. place the modified zip on your sdcard. i use
paint.net for graphics editing.
you might want to check the same directory within your systemui.apk file (/sdcard/system/app) to make sure whatever status bar icon you want to change has the same file name as the file you place in the modified zip above. just copy this file to your computer and change the extension to .zip, then open and drill down to /systemui/res/drawable-xhdpi/.
download
ZipThemer from the market. follow the instructions in the first post of above thread to update "edify" and build a flashable update zip using your modified zip file. make sure you select "yes" when prompted to make an undo file. this will create two new zip files on your sdcard, both will start with your zip file name, one will have "update" and the other will have "undo" appended to the end.
reboot into recovery (i use clockwork mod).
MAKE A BACKUP!
did you make a backup? if you did, then flash ("install from sdcard") the "update" file from above.
reboot. if you you run into problems on reboot (i.e., lots of FCs), then just reboot into recovery again and flash the "undo" file. if that doesn't fix the problem, then just restore your backup and you'll be back where you started.
please make a backup from recovery before you flash anything and don't blame me if something goes wrong

.