How to get a confirmation when deleting images?
I have a G4, and you're right. The Gallery app doesn't have a confirmation message, just a floating dialog that has an Undo button which disappears after a while. 

I'd recommend using another app instead. I use QuickPic. When you click the delete button, a popup with a delete icon appears. It serves as sort of a confirmation message. If you click the button, the picture is deleted. Otherwise, you can just cancel the operation by clicking the soft-key back button.