You could maybe rotate them 180° every frame. It would be a cheap effect but only require 1 sprite. Or you could change the explosion color palette to flash (or make the entire screen flash between yellow and red, passing by black, while the explosion shows up, but that might cause seizures x.x)
got purchases working...
can't help feeling it looks a bit suck**, oh well*EDIT*
just for fun, too many LRMs
(you can't have this many units in real life)