I wonder if someone here can tell me about some homemade projects where u have added lights to make the boombox more disco-like ?

My guess is that there are "few"

Some have added light bars (neon like) to the front of grills for glowing effect, other have replaced incadescent bulbs for white leds.

But what you'll find with the exception of a few people with skillz, that most will not mod or add things that don't belong, most like to restore to original factory condition.

Me.....I'm on both sides of that fence......if I mod something, it has to look like it was ment to be, if not, then I just restore to original functionality.

Also depends on the rarity of the box......basically........noone would modify a JVC RC-M90 box due to its rarity. All depends really......but overall answer to your question........very few