I would like to be able to set UV's directly in the MyBillboard class.
I have currently added it like this to custom DLLs:

In MyBillboard:
public Vector2? UV0;
public Vector2? UV1;
public Vector2? UV2;
public Vector2? UV3;

In MyBillboardRenderer -> GatherInternal:
...
myBillboardVertexData.V3.Position = (Vector3)vector3D4;
if (myBillboard.UV0 != null)
{
myBillboardVertexData.V0.Texcoord = new HalfVector2(myBillboard.UV0.Value);
myBillboardVertexData.V1.Texcoord = new HalfVector2(myBillboard.UV1.Value);
myBillboardVertexData.V2.Texcoord = new HalfVector2(myBillboard.UV2.Value);
myBillboardVertexData.V3.Texcoord = new HalfVector2(myBillboard.UV3.Value);
}
else
{
....
}
MyBillboardRenderer.m_arrayDataBillboards.Data[i] = myBillboardData;
...

Also this code ( MyTransparentMaterials.GetMaterial(myBillboard.Material) ) is used a lot of times and not very performance friendly. Being able to set a material reference directly rather than a string would be good