To make it transparent you need the transparent code;
material preset_#_tailMat
{
receive_shadows on
technique
{
pass
{
ambient 1.000000 1.000000 1.000000 1.000000
diffuse 1.000000 1.000000 1.000000 1.000000
specular 0.050000 0.050000 0.050000 1.000000 12.500000
emissive 0.000000 0.000000 0.000000 1.000000
cull_hardware none
cull_software none
scene_blend alpha_blend
alpha_rejection greater_equal 128
texture_unit
{
texture preset_#tail.png
tex_address_mode wrap
filtering trilinear
}
texture preset_#tail.png
}
}
}
}
Then when you're done open the tail file up in an art program and merge all the layers and then make sure to right click the layer and click "Make Alpha Channel" then erase the parts you no longer want; thus making it transparent.
It doesn't only have to be the tail. You can change whatever you want to be transparent so long as you have that code above. The tail one was just an example.
Still can't figure it out? Try some of these links located here, here, here and even what was linked above my post!