Portions of database icons can be made transparent so that the icon doesn't
make a perfect square. To do this, get into the edit mode for your database
icon. The dialog box for editing icons has two buttons on the bottom left that
look like pencils. The one that has little lines coming from the eraser-end
removes color. Click a pixel in the grid and it will be transparent, although
it will still look gray.
Transparent pixels in the editor have dark gridlines around them. Pixels that
have color have gray gridlines.
If you want to apply transparency to a larger area, click the button that looks
like a spray can, then click in the graphic color that you wish too make
transparent. This will apply the transparency to any contiguous-color pixels.