Sid Meier's Gettysburg - Opening Menus
The Opening Menu displayed is based on the last side played.
_n is for North played last otherwise _s for South.
open_n.pcx is displayed while loading and the right third of this remains displayed on the menu. The left 2 thirds of the screen is then taken from open_n2.pcx except for one of 6 horizontal strips which is taken from open_n1.pcx depending on the position of the mouse. Examples:
As the mouse is moved the slight differences between each image highlights which menu option will be chosen if the mouse button is clicked, but very different images could be displayed if desired. The right hand third of open_n1.pcx & open_n2.pcx are not displayed and can be blanked out.
For the _s versions the left third of open_s1.pcx & open_s2.pcx are not displayed and the horizontal strips are lower & on the right. open_s1.gif
I have made 2 templates to show the exact areas of these parts of the menu. Find them here.
All these files should use the same palette to avoid corruption. The palette should have the Windows colours in the usual places. After reducing your opening picture to 256 colours including the Windows colours, edit the palette to swap the Windows colours into the correct positions, then paste your picture into this once again.
SMA uses a slightly different arrangement.
SMG Design Tools Page