Lost as to where to start with a project...please help!
as far as i know, you need Adobe Media Encoder (or premiere pro...other vid software) to make flv files.irritatingly...i don't think you can make them in flash. which seems asinine.
if you have the mp4, you can open both the image and mp4 in separate Quicktime players then:
edit>select all> "copy" for the image
go back to the player with mp4 (be sure you're at the very first frame)
edit> "add to movie"
to save the whole thing as a new single file.
if you don't have those options in your quicktime player, you might need quicktime pro...which is like $20 USD for a license.