try this, but adjust the 640x480 to your screen resolution
convert \( zelda1.jpg -bordercolor white -border 15 \) \
\( -clone 0 -mattecolor black -frame 5x5+0+5 -blur 0x2 \) \
\( -clone 0 -shave 5x5 \) \
-delete 0 -gravity center -compose over -composite \
\( -size
640x480 xc: +noise random \) \
+swap -gravity center -compose over -composite \
zelda1_border4.jpg
or
convert \( zelda1.jpg -bordercolor white -border 15 \) \
\( -clone 0 -mattecolor black -frame 5x5+0+5 -blur 0x2 \) \
\( -clone 0 -shave 5x5 \) \
-delete 0 -gravity center -compose over -composite \
\( -size 640x480
plasma: \) \
+swap -gravity center -compose over -composite \
zelda1_border5.jpg
see
http://www.imagemagick.org/Usage/canvas/#random
http://www.imagemagick.org/Usage/canvas ... _gradients
also see tiling from some small image for the background
http://www.imagemagick.org/Usage/canvas/#tile
convert \( zelda1.jpg -bordercolor white -border 15 \) \
\( -clone 0 -mattecolor black -frame 5x5+0+5 -blur 0x2 \) \
\( -clone 0 -shave 5x5 \) \
-delete 0 -gravity center -compose over -composite \
\( -size 640x480
tile:tile_aqua.jpg \) \
+swap -gravity center -compose over -composite \
zelda1_border6.jpg