Bryan Tong Minh wrote once:
I don't know whether it is correct to assume that all files are /^(\d+)px-/. Subclasses of MediaHandler::makeParamString may return an arbitrary prefix not limited to /^(\d+)px-/. I think it is safest to simply move all files in the directory to the new location.
Or just delete it. I still can't understand if it's necessary to move them. They seem to be deleted by File::purgeEverything, so moving them is probably senseless at all. --VasilievVV