Template for 2Dunit100 bmp for SB Red Victory and Others in Series

[Sean]

I wanted to modify some unit pictures in the .bmp ,for starters in Red Victory.I tried doing it using cut and paste in XP Paint and had some success but my pictures are slightly out of alignment where the odd picture overlaps other pictures in game.Can I download a gridded empty template so I know exactly where to drop my pasted images?
I would like for example a lightly gridded box that has little spaces to drop all my pictures into the bmp.

A template for Red Victory would be cool,but other games in the series if templates are available I would be interested too.

Alternatively what method is suggested,I am not good with graphics and only want free programs and I sure other paint programs other than old XP Paint would be better.The reason I used XP Paint is because it is really simple interface,I do have WIN 10,but have not used the more modern Win 10 paint,maybe I should or Gimp maybe.
Ideas.