Ok, here's my wrapper for the Mac. How to use:
1. Download iPhoneShop-0.4.jar
here
2. Download the attached zip file and unpack (this is an AppleScript applet) and put on desktop or wherever you can access it for drag and drop.
3. Make a new folder anywhere you like and call it iPhoneShop. Move iPhoneShop-0.4.jar into that folder. Create a new folder inside the iPhoneShop folder and call it whatever you like (e.g. MyKeyboard or MyBarDialer). This is where you will put your modded pngs and the .artwork file.
4. Before you can mod the pngs that are bundled in the .artwork file, you need to extract them from the .artwork file. To do this drag the .artwork file onto my artwork applet (on the desktop). Let it do its thing and you will find a new folder called "pngs" inside the MyKeyboard or MyBarDialer folder right next to the .artwork file. This pngs folder contains the extracted pngs for modding. Go ahead and mod as you please.
5. When you're done, we need to transfer the files back into the .artwork file. Select the "pngs" folder and drag it onto my applet. Let it do its thing and you will have a brand new .artwork file for testing and/or distribution.
You can repeat these procedures as desired. The applet will automatically detect whether you are extracting from a .artwork file or stuffing a .artwork file from a folder full of pngs. In each case, the files will be overwritten.
I should add that I have only tested this with the BarDialer file, but the Keyboard should work the same. It's just a different filename. Let me know if you have any problems.