Panel Graphics Create & Edit

I've been working on PanelView and trying to make some graphic screens.  Are
their any favorite programs for creating and editing graphics for these
applications?  I'd like to be able to make nice accurate images like CAD but
be able to apply colors and size the image files.  Maybe draw in CAD, copy
screen, paste in paint, color, resize...  Or perhaps there is a paint type
program that will fill the need?

Thanks!

RogerN