Hi.  Thanks for writing Dimensions 2 Folders.   I sent a small donation and encourage others to do the same.  A few suggestions:
1: Dimension order:
It appears that the 9 x 16 option also captures 16 x 9?  It would be nice if there were a checkbox to tie the first dimension to width, 2nd to height? 
Why: to winnow out images that will fit on a hard landscape oriented device vs portrait

2: Only 1 identical image of same name
The current default of adding "(2),(3)..." to images of the same name is righteous.  However, a checkbox might engage feature to capture an "identical" file.  I think identical byte sizes would be good enough test for me, but of course to do it right, you'd want to do byte-wise comparison.
Why: So I don't have to find and delete identical files on my own

3: Folder replication
You have an option to recursively descend into source subfolders.  Maybe another option would recreate the same tree on the destination side?  When a new file is copied, if its relative folder doesn't already exist, create new folder(s) and then place copied file in same relative place.
Why: Because my wife spent a lot of time dividing things neatly into folders.

4: Size limitation
This one is tricky.  Basically copy no more than <specified> K bytes.  For extra credit either create additional folders and copy into them as needed or else allow for a second run to start where the first one stopped?  (It might have to work exclusively from suggestion #3 above.)
Why: to divvy source images for limited size media (4G thumb drives, for instance)