One word for things that would be nice to have, but not required to have?

Solution 1:

When people draw up budgets for their living expenses, they sometimes distinguish between necessities and nonnecessities, or between essential expenditures and nonessential expenditures. After paying for the necessary items, the person working within the budget may view the remaining funds as disposable income, and the things that he or she purchases with some or all of that leftover money may be termed (in a reasonably professional way) discretionary items.

Solution 2:

Desiderata ... but half your audience won't know the word.

Solution 3:

Consider the term complement

A thing that completes or brings to perfection

While the word has a connotation of complete, giving it a bit of essential tone, it is often used to convey something that it not necessary, but added on. A wine is not necessary to a meal but may be an excellent complement. Similarly, an accessory to a clothing outfit.

This is not to be confused with compliment, even though, as @Josh61 suggests, a hotel may give you a lagniappe that is a complement to your stay, with their compliments.