I hate the file requestors for Windows anything.  I've not found a decent file requestor yet that didn't make me pull my hair out.  So here's a request:

Size Lock, Position options, Default Display for type, Preview

Size Lock: I want the requestor to be as tall as it can be.  I don't care about width but it would be slick to see a way to lock the physical sizes down.

Position options: Under mouse, centered on screen, centered on parent application, docked left/right/top/bottom.  Self Explanitory

Default Display for type: If the majority of the files listed are of mimetype images/*, then display the content in thumbnails.  If the majority of the files are of anything that is not images/*, then display the default set.

Preview: Obvious.

Now, let's see this happen!