I'd agree with using tag bicycle_parking=stands
So far as capacity is concerned I'd tag the bank of stands in top picture as capacity=12. Each of the stands should take 6 bikes if they are parked correctly. Count the uprights - these stands are intended to accommodate 1 bike per upright. Too often the usable capacity is reduced by people parking bikes along the stands rather than straddling the stands - ideally in a nose to tail fashion to save handlebars getting tangled up.
As for the second picture I'd probably also tag it with 6 as the capacity - there are 4 uprights and at least a couple more bikes could be locked to the 'wheels' of the stand.