As far as I know the Maryport Epona is typical of the Epona representations in Gaul, ie a woman sitting side-saddle (not sure what sort of saddle they used, or bareback?) on a horse which is walking or trotting - not galloping or rearing anyway. Sedate. No other attributes, as far as I know.

What were the other Eponas from Britain - and are you sure there were none in Ireland? As a Celtic country I would have expected there to be some.