Photoshop TARGA Image Alpha [plus blood splatter]

Flatten your Photoshop file, but make sure you have an alpha channel.

Apply as a diffuse map.

Make these settings under Bitmap Parameters;

Select Image Alpha

De-select Premultiplied Alpha for better edges

Mono channel output: Alpha

INSTANCE a copy of this to the opacity channel:

This functions as a decal when you apply the material to a plane and raise ever so slightly above a wall, etc ... blood splats, etc.

Use the spatter brushes ... the larger the brush size, the bolder the
splatter effect:

This shows the Photoshop art with the alpha channel:

This is our rgb layer ... red:

Here we set up a brick wall and a decal as a 1x1 plane in front of it:

Perspective view: