Q1 - Try canola, it will keep the display lit, and you can play music. But no control on how long the slides go.

Q2 - Styrofoam, or wood. Make two little legs around the 770. Picture frame hack maybe? (I love the stand in the N8x0)

Q3 - This will be difficult, I have not seen any app like this (its like a Mac widget type thing right?)

Q4 - Transfer of photos over wifi... Many ways to do this. You can setup a FTP server on 770, use openSSH and SFTP, etc... SFTP is probably the best if you have linux, but even windows can do sftp (use filezilla). So look up SFPT and SSH.

hope i helped