Fill in emulator's dead screen space?

[jason]

I'm working on a home built arcade cabinet and its themed with decals on the sides and front. In the cabinet is a 27" (1920x1080) 16:9 monitor. Emulation Station fills out the entire monitor just fine with its UI. But while playing games, most are at the aspect ratio of the 80s\90s which I think is 4:3. This leaves empty, black space on the edges of the monitor. I was wondering if there is anyway to fill in those empty pixels with an image. I'm envisioning what it would look like if the entire 1920x1080 was filled in with a background image and then the emulator's 960x720 is placed on top of the background image.

I think this would look very cool and help complete the "physical theme" of the entire cabinet if I can do something with that empty space. I'm already experimenting with an ES theme to match the cabinet. I'd love to carry that over into the games also.

Is this possible? Does anyone have experience with this?

[herb_fargus]

@jason sounds like you're describing overlays.

https://retropie.org.uk/forum/topic/4210/using-custom-overlays-with-console-emulators

I'm surprised/not surprised it's not in the documentation. I've never used them so that's why it's not in there ;)

[jason]

This looks to be exactly what I need. Thanks for replying, I’ll dig into all of this info.

[asdfgasfhsn]

Overlays is totally what you're after @jason. It's a feature of RetroArch/Libretro so a large number of emulators available with RetroPie will have it available.

I've started compiling a list of links for customizing RetroPie builds. The overlays and shader section may be of help for sourcing overlay artwork.