How to make a decal trail? (Paper2D super meat boy style)

I’ve read through all of the unreal documentation on decals and can not get them to look right… I have this image

237965-slimetrail.png

(with paper2d filter applied) that is to be spawned behind the player while it walks so that it appears on the floor and walls of the map (a tile map) when pressed against them, similar to how [Super Meat Boy][2] looks yet my image always seems to turn out to be translucent and never the true colour of the image. The image also projects over my player as well, is there any way to work around this or maybe a seperate method that doesn’t use an image or doesn’t use decals that might be simpler?

Any input would be greatly appreciated.

Thanks in advance,
-Sparx