How do I design new images?

The images used for the buttons are standard 32 x 32 bitmap files.  You can create them with almost any paint program, including mspaint, that is included with most versions of windows.  Just remember to set the image size to 32 by 32. 
To run mspaint, click the button 

If you want the bitmaps to match the colors of your system, make sure that you use values of 192, 192, 192 for the button background when you draw it.

If you save your bitmaps to the images folder in the Program Files\TopDrop folder, you'll be able to select them quickly and easily.