What I'm basically requesting here is to be able to force the player to open( and see upon browsing folders ) files only of an extension I provide.

mob/verb/onlyPNGs( f as filetype(".png") )

mob/verb/onlyTextFiles( f as filetype(".txt") )

I know the same thing has been suggested by Jtgibson here, but seeing as that got no responses from anyone from whom it should have, I thought I'd go ahead and do a small "reminder".
That one's been a common request for a loooong time...
In response to Foomer
Ah, well, guess it's never bad to keep the request going till it gets fulfilled, eh? :p