I need help with the editor/suggestion

I am currenntly making a Deep Dip 2 inspired map called Edge Of Sanity, I've been working on it for about 3 months, 45 hours in and 950+ test runs etc.. I'd say that I am pretty experienced with the editor and everything, I even have custom items from the itemexchange plugin.

Now, my map is 99% finished, the only problem is that while it is day on the map, on the lower floors it is almost pitch black, I have added some light sources and it does help but it is not enough:

Does anyone know/have a big invisible light soure item/block or know how to brighten up the entire map??