Can ping flooding attacks still be implemented in a IPv6 network? And what could be a good way to simulate such an attack?
Yes, ping floods can still be implemented in IPv6 networks. They operate in largely the same manner they do in IPv4 networks. Although IPv6 is a "new" protocol (it was conceived in 1998), there's still plenty of attack vectors to worry about, such as the Neighbor Discovery Protocol and the massive address space IPv6 occupies.
As far as simulating attacks on an IPv6 network, I would set up a virtual network with your chosen OS and virtualization software, and use a suite like THC-IPv6 to attack the network. It is a suite used for attacking IPv6 networks. It's got all kinds of goodies. Smurf6 may be of interest to you.
If you want to do some reading on IPv6 security, this paper is full of good stuff.