This global graph suggests that most images load within a second up to the 50th percentile, and only in the 90th percentile do we start seeing 5-second load times, which seems acceptable. Should we be adding API loads or any other data to that number, to get the complete load times?

Instead of doing a straight addition of the existing data, I would prefer to find time this week to add a new metric measuring time from first thumb click to sharp image appearing, as part of this card of mine which has been left on the backburner for a while: https://wikimedia.mingle.thoughtworks.com/projects/multimedia/cards/430 I might not do preloading on proximity, but I'll at least do hover.