Hello monks,
Here's my latest effort, it's pure perl, so should run anywhere.

It is parametised so it will take the number of boxes in the output as an argument in the form:
 # perl blah.pl 19x20
(19x20 is the default)

This will produce a variable sized file (default is normally around 6Mb) called al.XXX (where XXX would reveal the surprise) in the directory from which it is run

                                                           $_=q^($w,$h
+)=s
             plit/x/,shift||"19x20";$q=10+10*$w;$r=20+10*$h;@m=((31,(1
+5)x
 ($w-1))x$h,(31)x$w);$m[$c]|=16,!(@a=grep!($m[$c+$$_[0]]&16+$|*$$_[1])
+,[-
 1,8],[1,1],[$w,4],[-$w,2])?$c=pop@p:${($i,$j)=@{$a[rand@a
 ]};$m[$c]&=~
 (8/$j);push@p,$c;$m[$c+=$i]&=~$j;++$u-$h*$w+$h||map$_&=15,@m,splice(@
+p),
 $c=$|=1}until$|&$c+2>$w*$h;$C=$q-4*int$q/4;$A=($q+$C)*$r;$u=pack"x"x(
+($q
 +$C)*$r);subZd{my($f,$g,$h,$i,$e)=@_;@a=sort{"000$a"<=>"000$b"}$h,$i|
+|$h
 ;for($a[0]..$a[1]){$s=($r-$_)*($q+$C)+$f;vec($u,$_,8)=$e||2 for$s..$s
++$g
 -1}};subZt{$a=shift;$x=10*($a%$w);$y=10*(2+int$a/$w)};dZ9,$q-20,10;dZ
+9,$
 q-20,$r-10;dZ9,1,10,$r-10;dZ$q-11,1,10,$r-10;map{t$_;if($_%$w){$m[$_]
+&2?
 d$x-1,11,$y:"";$m[$_]&8?d$x+9,1,$y-10,$y:"";}}0..-1+$w*$h;$F="LIST";o
+pen
 (FH,">al.avi");binmodeZFH;selectZFH;printZpack"V*",/\d/?$_:unpack"V*"
+,$_
 Zfor"RIFF",(1256+($A+24)*($B=3+scalar@p)),"AVIZ$F",1216,"hdrlavih",56
+,50
 0000,32,0,2064,$B,0,1,$A,$q,$r,(0)x4,$F,1140,"strlstrh",56,"vids",(0)
+x4,
 1,10,0,$B,$A,-1,(0)x3,"strf",1064,40,$q,$r,pack("vv",1,8),0,$A,(0)x4,
+pac
 k(("C"x1024),(0xff)x3,0,128),$F,(4+($A+8)*$B),"movi";map{printZSTDOUT
+"."
 ;t$z||1;$l=$x;$t=$y;t$_;$ri=$x;if($l>$x){$ri=$l;$l=$x}d$l+2,5+$ri-$l,
+($t
 <$y?$t:$y)-7,($t<$y?$y:$t)-3,1;$z=$_;print"00db".pack("V",$A).$u}@p,(
+-1+
 $w*$h)x3;print"idx1".pack"V",16*$B;$o=4;for(1..$B){print"00db".pack"V
+VV"
 ,16,$o,$A;$o+=$A+8}^;s#((?{$a.=$+})\s?(\S*)\s?)*#$a=~s/Z/ /g;$a#see
[download]

(that's supposed to be a clapboard btw!)

If there is enough interest i'll write a deobfuscation/explanation of what went into it,
I've written a clean version here.

In the meantime some of my references and some other notes are in the spoiler below:

I hope you all enjoy it.
Alex
update: Add link to explanation.
Also use V not L (see this) to force correct endianness - this should now work on mac's
and fixed a bug where it didn't work for 5.8.8