See, there you go again, PureX.
Your mixing up different categories here. "Art" is an attribute or a process, but there is no actual "art" that exists as a distinct entity. Yes, we use it as a noun to say "this has the attribute we call art, therefore we call it art". No one is asking you to identify what counts as art and what does not. We are simply asking you to explain what you mean when you say "god". Just as you could explain art as "(the creation of) beautiful or significant things". Yes, the decision whether or not something is beautiful or significant and could therefore count as art is subjective, but the definition of "art" is not something mysterious - in fact, it's quite trivial.
I'll try this again: what do you mean when you say "god"?
If you think "god" is like "art", then can you really say you're talking about something that exists beyond the conceptual level? Then does "interesting" exist as well? Yes, things that are interesting ("thing od interest", if you will) do exist, but that's not "interesting" itself - "interesting" is purely conceptual, just as "art" is (not the actual things we determine to be art). Just because you can use something as a noun doesn't make it any more special and it does not make it "exist" any more than any other concept. That goes for all your favorite nouns - love, art, justice, etc...
If you're trying to say that god exists on that level - then I might agree. Of course, so do flying reindeer.