What's a good one-stop-shop pedal for ambient textures?

WTB22

Take a look at the Chase Bliss MOOD, Hologram Microcosm, Strymon Nightsky… All quite complex units but they would all work perfectly in different ways for what you’re describing. 

Wazmeister

EQD Avalanche Run.

mark_jwedge

GFI synesthesia might be worth a look

distressed

Hologram Infinite Jets

Secret_Sam

Line 6 m9?

TheMarlin

OBNE Black Fountain. One of my all time favourite pedals. Fantastic for ambient textures.