I agree with the keepsakes, or maybe a special little outfit.

I didn't have a shower or sprinkle for my second, but she also didn't get many gifts when she was born. I look at the stuff DD1 got and what DD2 didnt get and there is a huge difference. In the end I felt bad and went and bought a heap of special little albums/frames etc.

Another idea is money towards a second car seat, maybe from a group of people.