I can hide inside the image of a barrel, right?

I'm sure this has come up before: I can cast Minor Illusion to create the illusion of a large barrel or box or whatever, and then hide inside the image (I'm a gnome, so shorter than 5').

Enemies would specifically need to take the study action to determine the barrel isn't real, at which point I'd be visible to them. But until then, and for the next minute, I could be firing my crossbow (no verbal component to give away my position, though I suppose the twang of my crossbow might be audible). 

Similarly I could hide our bard or an NPC, right?

Yes, that should work, and it's a common use of Minor Illusion. 

However, depending on what sort of enemies you're fighting, it may not be reasonable to assume that they won't figure out roughly where you are after your first attack.

Quote from MongooseGef >>

I'm sure this has come up before: I can cast Minor Illusion to create the illusion of a large barrel or box or whatever, and then hide inside the image (I'm a gnome, so shorter than 5').

Enemies would specifically need to take the study action to determine the barrel isn't real, at which point I'd be visible to them. But until then, and for the next minute, I could be firing my crossbow (no verbal component to give away my position, though I suppose the twang of my crossbow might be audible). 

Similarly I could hide our bard or an NPC, right?

 Probably any short creature could hide. Your DM might make you roll a stealth check to stay hidden (especially after firing the crossbow), but it could work, especially for an ambush of some sort.

Yeah, an ambush is what I'm expecting this tactic to be used for primarily. Anything to give me an extra round or two where I can attack but the enemy can't!

You can hide, but there's some ambiguity as to what you can do without revealing the illusion. The way I see it, shooting through the illusion counts as physical interaction. If someone sees a bolt fly through the object, they will know it's an illusion.

Quote from MongooseGef >>

Yeah, an ambush is what I'm expecting this tactic to be used for primarily. Anything to give me an extra round or two where I can attack but the enemy can't!

 If you attack through it, they will know it is an illusion. I've used minor illusion to hide my gnome druid at low levels but the monsters we have fought the last few levels (we are 10 now) are way to smart to fall for the trick.  maybe if you're in a room full of barrels (mimics used that trick in a different campaign)...even then maybe not.