Back in MAME 0.163 I was able to make custom backgrounds that mimic the original hardware display of non-lit objects for handheld games.
With the custom background on, I can play it as well as I used to on the real thing. I still have it, and I feel it's pretty close to how it actually displays.
When I finally updated to the current latest version MAME 0.188 to check out the latest handheld emulators, I'm not able to reproduce the same background effect. The game is significantly harder if I can't tell where the discs are moving on the second stage.
There are more custom backgrounds I'd like to make for the Tiger and Konami LCD games. The older version required artwork files in the artwork subfolder, and the new one just uses the svg file from the 7z. I've tried modifying the svg file, but it complains that the file has an incorrect length.
If it's not possible to make a custom background, I would like to present my case that it should be a feature. I know the non-vector backgrounds are missing, but if you see how Nintendo implements Game & Watch simulations for GBA and DS, they have the same effect of faintly showing non-lit objects. Many unofficial simulations of handheld game have the same feature. I think it would be great if you could have the option of showing it, maybe even adjusting its visibility up and down like you could in real life by adjusting the angle of the display. I understand it's debatable whether or not the creators intended them to be seen or not, but I find these types of games are much harder when I can't tell what the intentions of possible movement are.
The custom background for tmtron is attached if anyone wants to try it out.