Pressing 1 – 4 to select characters is a good idea. Makes the game a lot easier to manage rather than having to select each characters icon.
Up and Down arrow keys (or W/S) to scroll the screen up and down as well as the mouse being a the edge of the top and bottom of the screen to scroll.
Custom key bindings would also be useful both to show what keys do what by default and to let people make keys do other things.
A quick tutorial would also be good. Maybe in the form of “place all 4 characters are is unsafe, here is how to do some things” and then let those things allow you to get to the start of the game.
Feeding in to the tutorial idea just above, at least for the first level or two being able to mark useful resources for the chopper and barriers so that you know what is useful for those particular things
Easier way to tell what items are what. Found myself not knowing what sprites were until I picked them up. Would make things difficult for new players.
Easier way to transfer items. Found myself with characters with full inventories. A verbal message or text fade in – fade out message that mentions that another character has space for that item would be good.
A clock or bar, etc that shows what time of day it is and how long until night so that you know when the hostiles will start their assault would be useful.
An option to go full screen is always good.
Volume options as well as at least brightness/gamma options and the ability to save/pause/reload is good.