Customization of the consent page is a really good idea that has been on our radar for a while. Please track [oxAuth issue 300](https://github.com/GluuFederation/oxAuth/issues/300)
If you want to display the last login time, you could perhaps do it today using a two step authentication flow, where page 2 is the informational display, that automatically submits after a few seconds. Or you could also perhaps use some javascript that communicates with a backend web service in a one step authentication flow.