Could a veneer or crown be an option for an indented/crooked premolar? (Photo)

From the information you have given us here, It may be possible to put bonding or a porcelain veneer on the outer aspect of this tooth to make it appear less crooked and more natural in the smile. I do not advise this as a first choice as it could over-contour this tooth and make it more susceptible to cavities and gum issues etc. My advice would be to reconsider an orthodontic consult if even just to re-position this tooth to correct the occlusion and appearance.  If orthodontic treatment is not an option, then bonding or a veneer can treat the aesthetic issue without treating the issue with the general positioning of this tooth. In my opinion, a full crown here to correct the positioning would require significant removal of tooth structure that can compromise the tooth in other ways- I do not think that would be a very good idea. Hope this helps. 

You can do whatever you wish to do if you can find a dentist that will go along with your plans. You are or were already doing Invisalign to straighten your teeth and bite, if you are impatient then you could do a veneer to make that premolar look even with other neighboring teeth (build out the “buccal corridor”). Adjacent teeth may need to be adjusted slightly to achieve a better proportions amongst the teeth so that one premolar don’t look skinnier. Again, find yourself an experienced cosmetic dentist, a porcelain or lithium disilicate veneer will do wonders. I do not recommend a composite bonding for this purpose.

It looks like you already have "buttons" on your teeth from Invisalign or something similar. The tooth also appears to be slightly under erupted. If your dentist is moving your teeth I would stay the course -- he/she is trying to make room for that tooth to get into position. I don't feel like a veneer or crown would be the solution here. Good luck with your journey!