I don't have that case. But just from looking at the photos it looks like a pocketed flap (possibly zippered?).
I would put small, easy to lose items such as adaptors, dripping atomizers, cartomizers, spare drip tips, a
tank accessory tool, and maybe some Q-tips to clean the center post out when it gets
juice in it.
Nothing easily breakable (clearomizer or
tank), as once the case is closed, all the hard objects (the mod and batteries) are going to be firmly pressed against it.
You would be surprised how much stuff you can pack in these cases. Here's a pic of mine. I don't normally pack that much stuff, but put a lot in there just to show how much it will hold. I use the case from Smokeless Image for their eGo sized X2 batteries.
Smokeless Image | The Best Electronic Cigarette

