Would you be willing to share what else is on the radar? Might save your having to answer a lot of individual questions (like the following
Personally I would like to see the ability to different ways - by date, name, etc.; and
in particular to sort pictures by date taken.
And by way of feedback let me say I like the overall layout but something seems clunky (or unfinished
about how one interacts with the files in a list. Long-press to select seems odd - I would expect a button that brings up the checkboxes, and I would expect long-press to bring up a menu of operations, or perhaps the file properties. I think long-press is too valuable an interaction tool to be used this way...
Finally it seems a little odd to me that the first button brings up a submenu. I would expect to see the most common operations all on buttons and the least on the "..." menu.