I just pushed an update that changes the behavior of how the “Start Render” measurement works. It used to mark the time at which something could display on the page (the content dimensions would be non-zero) but it didn’t mean that anything was ACTUALLY displayed.
The update moves the measurement to when something actually gets drawn to the screen for the first time. I can’t guarantee that the “something” is anything the user cares about (css background image for example) but I can guarantee that it is the first time that anything gets rendered to the screen. I also added in a screen shot of what the screen looked like at the start render time so you can see what was displayed (if it looks blank it isn’t really, may just be compressed-away by heavy jpeg compression of the screen shot or your background color is just off-white).
I also added in a screen shot for the “DOM Element time” so you can see what the screen looked like at the time that measurement point was registered but that measurement doesn’t get a lot of use.