Can the noun “sheen” denote the simple outward appearance of something?

Solution 1:

I checked a handful of dictionaries. Like you, I couldn't find a more figurative meaning for sheen; the definitions were all more focused on a literal shine on the surface of something.

That said, we use many synonymous words – such as shine, glow, and luster – figuratively. When we say things like:

Her face shone on her wedding day.

Robert was glowing when he brought home his report card.

The university has regained some of its luster from yesteryear.

we don't expect that the bride's face would have literally lit up a room, or that Robert was glowing green, as if he had just walked past a radiation leak, or that the campus banisters had been recently polished with brass cleaner.

Such figurative uses of the word sheen don't seem completely rare. Among Wordnik's usage examples, I found:

My favourite Sci-Fi shows are all American, although maybe there's a certain sheen added by cultural distance. (from a comment on a blog)

It finds [Courtney] Love's songs buffed to a chunky rock sheen in search of a commercial audience, just in time for some putative grunge revival. (from a record review)

The Limits of Control is all surface and no substance. Talented cinematographer Christopher Doyle lends a glossy sheen to the proceedings, but it all adds up to little more than an in-joke for the artsy clique. (from an online film review)

So, to answer your question, I'd aver that your example is fine. Moreover, as I mentioned in my comment, there are hundreds of instances of that particular phrase in published works already, as well as others, such as sheen of honesty and sheen of virtue.

Solution 2:

As @JAM stated, you would normally expect to use the word 'veneer' but 'sheen' is used as well. You will be understood.