Hell yes!
I remember having a similar addon that adds the soundtrack to the main and brick selector menu, and ghost brick sounds. You, my friend, have completed the package!
EDIT:

That's not right.
I found all this mess in the console
Client checking Add-On: Client_LegoRacersGUIMod
Loading Add-On: Client_LegoRacersGUIMod (CRC:-1297372237)
Executing Add-Ons/Client_LegoRacersGUIMod/client.cs.
Executing Add-Ons/Client_LegoRacersGUIMod/gui_audio.cs.
Activating package: LR_GUIMusic
Activating package: LR_GUIAudio
Executing Add-Ons/Client_LegoRacersGUIMod/ui/MM_Blockhead.gui.
ERROR: function declaration failed: MainMenuGui::onWake
Activating package: MMBlockheadDisplay
...
Could not locate texture: Add-Ons/Client_LegoRacersGUI/images/btnStartServerLR_n.png (download failed, using default texture)
+- using blank texture
Could not locate texture: Add-Ons/Client_LegoRacersGUI/images/btnStartServerLR_h.png (download failed, using default texture)
+- using blank texture
Could not locate texture: Add-Ons/Client_LegoRacersGUI/images/btnStartServerLR_d.png (download failed, using default texture)
+- using blank texture
Could not locate texture: Add-Ons/Client_LegoRacersGUI/images/btnStartServerLR_i.png (download failed, using default texture)
+- using blank texture
Could not locate texture: Add-Ons/Client_LegoRacersGUI/images/btnJoinGameLR_n.png (download failed, using default texture)
+- using blank texture
Could not locate texture: Add-Ons/Client_LegoRacersGUI/images/btnJoinGameLR_h.png (download failed, using default texture)
+- using blank texture
Could not locate texture: Add-Ons/Client_LegoRacersGUI/images/btnJoinGameLR_d.png (download failed, using default texture)
+- using blank texture
Could not locate texture: Add-Ons/Client_LegoRacersGUI/images/btnJoinGameLR_i.png (download failed, using default texture)
+- using blank texture
Could not locate texture: Add-Ons/Client_LegoRacersGUI/images/btnPlayerLR_n.png (download failed, using default texture)
+- using blank texture
Could not locate texture: Add-Ons/Client_LegoRacersGUI/images/btnPlayerLR_h.png (download failed, using default texture)
+- using blank texture
Could not locate texture: Add-Ons/Client_LegoRacersGUI/images/btnPlayerLR_d.png (download failed, using default texture)
+- using blank texture
Could not locate texture: Add-Ons/Client_LegoRacersGUI/images/btnPlayerLR_i.png (download failed, using default texture)
+- using blank texture
Could not locate texture: Add-Ons/Client_LegoRacersGUI/images/btnOptionsLR_n.png (download failed, using default texture)
+- using blank texture
Could not locate texture: Add-Ons/Client_LegoRacersGUI/images/btnOptionsLR_h.png (download failed, using default texture)
+- using blank texture
Could not locate texture: Add-Ons/Client_LegoRacersGUI/images/btnOptionsLR_d.png (download failed, using default texture)
+- using blank texture
Could not locate texture: Add-Ons/Client_LegoRacersGUI/images/btnOptionsLR_i.png (download failed, using default texture)
+- using blank texture
Could not locate texture: Add-Ons/Client_LegoRacersGUI/images/btnCreditsLR_n.png (download failed, using default texture)
+- using default 'red' texture 'base/data/shapes/red.png'
Could not locate texture: Add-Ons/Client_LegoRacersGUI/images/btnCreditsLR_h.png (download failed, using default texture)
+- using default 'red' texture 'base/data/shapes/red.png'
Could not locate texture: Add-Ons/Client_LegoRacersGUI/images/btnCreditsLR_d.png (download failed, using default texture)
+- using default 'red' texture 'base/data/shapes/red.png'
Could not locate texture: Add-Ons/Client_LegoRacersGUI/images/btnCreditsLR_i.png (download failed, using default texture)
+- using default 'red' texture 'base/data/shapes/red.png'
Could not locate texture: Add-Ons/Client_LegoRacersGUI/images/btnQuitLR_n.png (download failed, using default texture)
+- using blank texture
Could not locate texture: Add-Ons/Client_LegoRacersGUI/images/btnQuitLR_h.png (download failed, using default texture)
+- using blank texture
Could not locate texture: Add-Ons/Client_LegoRacersGUI/images/btnQuitLR_d.png (download failed, using default texture)
+- using blank texture
Could not locate texture: Add-Ons/Client_LegoRacersGUI/images/btnQuitLR_i.png (download failed, using default texture)
+- using blank texture