LED's, Decals, Shopped - etc are all basically case by case bases depending on what buyer is looking for.
When I am getting a game ready to sell the first thing I do is to be sure everything works 100%, boards look good or are repaired as necessary, harnesses repaired & boards repined as necessary, machine is cleaned up as good as possible but completely as found as far as touch up etc., And then I either fully shop or lightly shop the machine depending on how dirty playfield is and how nice machine is overall.
Once done I play & enjoy every machine for at least a month. At that point I decided if I like it well enough to replace something in the collection or if it gets sold. (Since our space is limited to about 25 to 30 machines and space is always fully every machine I buy now has to replace something else if I decide to keep it long term).
I don't believe in doing a ton of cosmetic work on machines - I feel the buyer will know better exactly how far they want to go with that. I don't add LED's - again everyone feels differently about them. I don't do a lot of mods or add a lot of unnecessary stuff - just make sure game plays great and looks good.
My thoughts are "over the top" might be going to far for the buyer so why do it? Do a nice job and price machines accordingly!
Just my 2 cents on how far is too far.