I use Stretch with MATE as desktop.
My current icons are from /usr/share/icons/hicolor/48x48 .
I have multiple configurations of some programs installed.
I would like to use icons that are semantically related.
I would like to use custom icons that are 48 high X 96 wide.
These would be created joining two 48x48 icons side by side.
Would the MATE panel &/or desktop accept these?
Assuming it would, is there a simple graphic program that would accept
to identically formatted images and place them side by side in a new image?
If MATE cannot accept rectangular rather than square icons, I suspect I
can create an app that can (I think I've seen Tcl/Tk that could be adapted).