when the amiga powers up, it doesn't know how to send a display to the GFX card, so you won't get anything. when CyberGFX initilises the librarys, it'll dump an image into the card's GFX memory (probably saying something like "CyberGFX V3" at 640x480x8 31Khz 60Hz) via the CGXbootpic.library (CGX V3) so at least you know your card is working....
that is provided you have the CGX tool types set to "BOOTPIC=1"
CGX V4 has the bootpic built into the main system library (i seem to remember), but you still need the tool type set.
otherwise you won't get a display untill the displaymode via screen mode prefs is activated, or you start playing around with CGXmode to start finetuning modes for your monitor.
the amiga won't display to a GFX card as per default, hence the picassoIV people building in a scan doublerso you got a display no matter what.
took me a few evenings to figure out when i got my CV64/3D but its a piece of cake when you know whats going on.