There are many, many options. Over the Em - C - B7... progression you can use the E Harmonic minor scale - works really well and sounds exotic.

Usually, you can think of the minor pentatonic as kind of a shell - something you can almost always use. But then you can add notes as extra flavor here and there, and you don't have to think - "oh, now I switch to this scale". Just use your ears and try to find certain flavor notes that give you the sound you want.

Exotic sounds usually come from playing

• The major 7th in a minor key - like in the harmonic minor scale.
• The sharp 4 - like the lydian scale. Or play the Blues scale, but skip the 4th, just keep the b5 and the 5th.
• The b2 - half step above the root, like the phrygian scale, or phrygian dominant scale. Very dark sound.