I don’t think that the options from Google or Glosbe are appropriate.
This use of Imagine as an exclamation that introduces something that someone should see in their mind (and potentially find it exceptional) strikes me as a little bit particular and not something that has a good one-to-one translation into Bambara/Jula.
If you really want to use a verb in a similar way, how about using the verb bisigi and an optative construction with ka:
I k’à bisigi ko…
“(You should) Imagine that…”
Otherwise, I think you could probably use the noun kabako in your examples. For instance: