Seeing the ways the biomes merge has been one of the most interesting things with my rental experiments. 
Gleam Lake seems to be able to merge into a number of biomes that go higher up. Some merges I know for sure-
Sky Pattern - Creates big vertical walls of gleam, but they’re broken up a bit usually, and sometimes encased in thorns.
Island Trees - Good results here, get some nice farming areas where it covers the top of the canopy then merges into a solid ball sometimes.
Floating Shrapnel - Gets the largest areas of gleam I’ve seen, though not really a deep layer.
Alien Invasion - Gets layers of gleam in the “spaceships” but be careful with this biome, seems to get a really nasty surface biome along with it, tons of twisted trunks covering the ground (though this one MIGHT work well for rubies, I need to test that).
Some general biome notes-
Coral Sea - This is the one that gives clumps of gleam in the ocean. Really pretty though not good for farming. But a nice choice for looks on your world.
Island Trees - Though not good for any gems, one of the most useful farming biomes I’ve found. Tons of trumpet roots and glow caps (edit, at least for T5+), and obviously the lustrous wood.
Trench - AVOID!! Unless you’re going for an underground lava cavern lair, maybe for that it would be useful, otherwise, this can totally ruin a lot of your planet for mining and create deathtraps everywhere.
Stone Ball - This creates some great topaz farming spots. Pretty one, too. If you get a Shock T6, take this for lv 8.
Giant Slice - Will give some nice building land on a higher tier world. 
Haha, almost tempted to do a Build Archetype thread in a month or so, once I get an even better feel for these. Do screenshots of biome selections and what they can produce, what they’re good for.