FlexHEX contains a set of icons you can use to assign icons to toolbar and menu buttons using the Customize command. If you wish you can replace the standard icons with your own. To do this, follow these steps:
Create an icon file and name it UserImages.bmp. The file must contain all your 16x16 icons side by side, that is the bitmap dimension must be 16*N pixel horizontal (where N is the number of icons), and 16 pixels vertical.
Fill all the areas that must be transparent with the gray color RGB(192,192,192). The resulting file should look like
Place the file into the FlexHEX directory (typically C:\Program Files\FlexHEX) and restart the program.