1) Make a generic suggestion thread? I am surprised that at this time there still isn't one.
2) While in dungeon, display the cost of preparations currently used and current amount of kingdom gold. This is so you can hit Restart button while using preparations and not be like "geez I wonder how much gold I have wasted already... inb4 I come home and see an empty vault".
3) It might be benefical to add some way to check out what's in your locker while you're in dungeon. This is so if you come across a shop with some interesting item that is useless to your current run, but could be used for later as a locker prep, you don't go all "HMM does my locker have this item or it doesn't? derp I don't remember"
4) It appears to me that no matter how much bosses there were in the dungeon, you can carry out one and only one trophy, and it's the one you were standing on when you hit Exit button. If this is the case, tell the player in-dungeon the market value of the trophy he is currently standing on. So you don't go all "hmmm... does the warlock beard cost more gold at taxidermist... or was it nose ring... don't remember"
5) Remove/add an option to remove the popup warning that tells you "Your vaults are full!" and appears every time you hit the tavern. I have a tendency to not spend money at all, and therefore every so often I have to go to some random dungeon, grab all the preps I can, and massively suicide the character at step 1 just to lower the amount of gold in kingdom and get rid of the annoying popup. Seriously, a one-time warning when I first hit the cap and displaying the gold number in red ever after is more than enough.