Why a separate table? Separate from what?
Image is saved into an Attachment field?
This is interesting. I get the same behavior. Unexpected.
The image is still in field and if I pull field from Field List, it will install Image control on form bound to field and display image.
Something else I never noticed before. Image control installed by pulling from Field List has Enabled and Locked properties whereas control pulled from Design tab does not and there are other property differences. Also, DLookup does not work at all in the Field List control. Users can interact with the Field List control but not the other.
But as you say, the DLookup will no longer pull the image until it is re-uploaded.
Can't you just include logos table in form RecordSource? Otherwise, a subform for image may be only solution if you want to keep images embedded in table.