So after long time I will tell how to make flash screenshot. First of all we will need few dependencys:

• Xvfb - will be our virtual screen
• gnash or flashplayer it will open our flash file
• ImageMagic it will make screenshot and some other tasks

That's it. Let's go to do some testing.

 Basic idea is to run Xvfb, then in virtual desktop run gnash or flashplayer and make screenshot with ImageMagic.

./xvfb-run.sh --server-args="-screen 0, 1024x2730x24" ./screenshot.sh

xvfb-run.sh file can be downloaded from http://svn.exactcode.de/t2/trunk/package/xorg/xorg-server/xvfb-run.sh

So, how does looks like out ./screenshot.sh file content:

#!/bin/sh

#we use gnash this time
gnash --hide-menubar -r 1 ./13.swf &
#./flashplayer ./05.swf &

# we wait till flash loads
sleep 15
import -window root screen.jpg
convert screen.jpg -fuzz 80% -trim +repage -crop +0+30 screen_cropped.jpg
pkill gnash
#pkill flashplayer

I add crop of 30px because I do not want that our gnash menu bar in this case be visible. That's all. You will have nice flash screenshot.

Update 2

Benjamin Wolsey noticed that since 0.8.7 version. gnash has native screenshots support. So all above code can be reduced regarding gnash native screenshot capabilities.