We hear that it is good to have a theme for your dungeon. But I don't think "theme" is something that should be randomly rolled or determined by procedure. I think the theme for a dungeon or adventure is the initial seed you have for it; it should be an intrinsic thing, not an extrnal template you apply to it. (though you may have some success with thinking of the theme you do have as a template to apply to specific places and things and situations)
The theme hsould be what has inspired you in the first place. It must come from that ineffable wellspring that is inaccessible to reason, that sheds introspection and application of rules. with any luck, if you have a good theme, it will bleed through your process.
a theme is not "goblins" or "red" or "death" or even "grief". a theme is nuanced, it has dimensions on multiple axes. it evokes and generates situations all on its own. it implies directions and relationships.
at least, this is how i feel when i look at a "table of themes" and it looks like a flat wall of cliches to me. A pile of unfinished wood blocks.