It would be very useful to be able to see the texture in the light materials slot. I work with alot of retail installations and its impossible to know which POS graphic is where unless you render.
If there is a way around this id be glad to hear it!
If you set the colour from White to Black in either the CoronaMtl self-illumination or CoronaLightMtl then set the material to “Show Shaded Material in Viewport”, you should be able to see the texmap in the viewport without needing to render it.
If that’s the case, you could always just save a copy of the CoronaLightMtl and CoronaMtl to a custom matlib where your ideal settings are already saved then just used that as a template for new materials than a regular corona default.