The game will find any .material file inside of the game that lays within the folders added to resources.cfg as far as I'm concerned. So with other words, if you place your .material file inside of my_objects folder where it should be, and then try to add your ice material to a mesh from within the game it will work.
Do keep in mind though that in order to add your own material to a mesh the coding for such material within your .material file must be written correctly, but you must also give the correct name for the material in the game which is not the name of the file, rather the name you give the material in the coding.
Something like "IceMat" all depending on what you name that line, I also do believe it's case sensitive so if you write IceMat it cannot be icemat, then the game object maker will not find it.
Look at the line for the texture in the crystal.material that comes with the game:
material crystalMat
{
technique
{
pass
{
cull_hardware none
cull_software none
emissive 1 1 1
texture_unit
{
env_map spherical
texture crystalTex.jpg
}
}
}
So if you were to add the crystal material onto any object, you'd need to give the game "crystalMat" as your material. Hopefully this is correct since I haven't diddled around with it in some time now.