Users might start at picture 33 of 55. Slowly advance till 55. And then want to see the rest.
At this point all they can do is go backwards one by one until they notice they are finally back before 33 and into new territory.
Therefore please at least add "|<-" and "->|" controls, to get them to the first, and last, in a hurry.
And maybe even add    ...    ... or whatever further shortcuts to help them get to more places in the sequence.