Digital Light & Color

The red outline on depressed buttons is helpful, but a little faint. Perhaps tryout a somewhat thicker line?
Under File, I use Open from Default and Save to Default far more that the rest combined. It would be nice if they were at the top of the list, or the list order of file operations could be customized, or if there were (lefthanded so my right hand could remain on the mouse) keyboard shortcuts for these two operations.
When saving a file and you type the file name plus extension, it would be nice if the file type would automatically become that of the extension rather than requiring the extra step of choosing the file type. (The reverse does this. If you pick a file type, the extension on a file name automatically becomes that of the the file type.)

For the next release, I added an item to the Theme dialog box to let you customize the depressed button border color.

Making the extension change the file type would be hard to implement and is not standard Windows app behavior.

There are almost no keyboard shortcuts left. One other thing -- if you do a File Open (or Save As), the Navigator pane at the left edge of the File Open (or Save) dialog box includes a Picture Window item with the default folder below it.