Under Core/sprites/weapons/weapon effects there's another laser projectile (unfortunately it's broken) if you open it in Spray you'll see there's a nice ammo crate image.
Make a copy of the wooden crate sprite in containers and rename it ammo_crate, in Spray open up the laser sprite above and export the image and pallette as raw and act files.
Then open the ammo_crate sprite you just made (in spray) and import the raw and act files.
Then change the Sprite header info (at the top) to
Depth 3
Height 1
Width 2
Center?(x,y dword) 146 198
and the Directions/bounding box info (under the image) to
Left 135
Top176
Right 164
Bottom198
Width 29
Height 22
save it and you've got an ammo crate to store your ammo in
To make the tile use Redviewer to extract the image as a TGA, open up the tga in your graphics software and save it as a png.
Convert the png to a zar with the editor and use Redviewer to make it a tile.
