I'm not sure which verb to use in this sentence - do or does? Your thoughts appreciated! I think the problem is that the verb refers to a singular and plural noun.
How does the imagery
How do the metaphors
Combined, you can use either as long as you use the correct one first.
How does the imagery and/or metaphors used evoke suggestion?
How do the metaphors and/or imagery used evoke suggestion?
Since you have two subjects, then
evoke will always be in the 3rd person form.