Well, "best" and "easiest" are subjective -- and often contradictory!
You can make an image dynamic by clicking it and choosing Make Dynamic. This is GUI-driven and probably "best" for you. Of course it has to be linked to a Segmentation or it won't work -- so you're getting ahead of yourself if you don't already have a Segmentation + Segments set up to address the "depending on the customer" part.
You can use Velocity to output <img> tags directly. To me this is "best" because I've never been fond of the Make Dynamic experience, and it doesn't require a Segmentation. But you have to be comfortable with at least basic Velocity coding.
Also please turn off Caps Lock, thanks.
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