Here's another of my control panels. Not one of my layouts though, but the latest project by the Sussex Downs 009 group - and at about the size of an A4 sheet of paper, the largest I've made.
The principles are the same as most of my layouts though, DC "cab control" (two controllers) through colour-coded sections, which are mounted along with point switches on a mimic panel. The panel is a sheet of 2mm aluminium onto which is mounted a printout of the diagram, and covered with a sheet of clear plastic - 20 thou sheet in this case due to the size, but thinner packaging plastic does smaller panels. So, now we just need to wire it up.