I promised new generators. Luckily several people sent some in. So there is a pretty long list:

• PaintStand from Jens Persson is a stackable stand for small paint bottles based in this video from Tested.
• CardBox also from Jens Persson can house a number of playing card decks and features a nice slide in lid.
• TwoPiece is simple box with another box as a lid that slides over the first one. While I rewrote large parts of the generator the idea and first implementation was submitted by bobm123 quite a while ago.
• DisplayCase from Alexander Bulimov is a simple closed box optimized to be cut from acrylic for displaying small objects.
• RoyalGame of Ur is an ancient board game featured in this video from the British Museum
• LaserClamp can hold warped plywood down on a knife table. This already kinda works but it will probably still change form to work more conveniently.

Additionally some old things got improved:

• Most flex boxes now have a latchsize parameter to allow cutting them much smaller
• Cabinet hinges can now be mounted on the outside of the box
• The HingeBox supports a split lid that opens to both sides
• The move parameter in the parts API now supports "mirror" to make rendering  symmetrical parts easier

Update:

I got pictures for at least some of the new boxes / generators:

PaintStorage (by Blancanegra)

CardBox

TwoPiece

DisplayCase (by abulimov)