How bloated do you want the game's file size to be? Text game first, image browsersecondprobably way lower. Smutosaur has the full size images. Look there.
Larger versions of stuff will be available as part of the fabled ~imagepack~ version of the game. Eventually. One day.
If I'm not wrong those bust that we got current ingame are about that size actualy so there isn't any larger versions of them hidden in game. So making option to expand them would mean add all the pics bigger version that would...again bloat game file and that isn't as I suppose point of your suggestion Atticus.
On small screens, like phones, they are shrunken down considerably.