This is an interesting question, because actually I think this is rather a depressing play, and its themes are certainly no exception. So, to try and identify an "appealing" theme as your question puts it is a bit of a challenge. I suppose one theme that we could look at and develop is that of growing up and gaining independence. This is something that of course Tom finally gains at the end of the play as he leaves his mother and sister and, much like his father before him, breaks out to live his own life free from the ties that he feel oppress him and prevent him from discovering and expressing himself and who he is.
I am trying to couch this in positive terms, but the truth is that even this "victory" for Tom is bittersweet, as he himself reflects in the final lines of this play. He talks about how something will remind him of Laura and how he is unable to escape her:
Oh, Laura, Laura, I tried to leave you behind me, but I am morefaitful than I intended to be! I reach for a cigarette, I cross the street, I run into the movies or a bar, I buy a drink, I speak to the nearest stranger--anything that can blow your candles out!
Even though Tom has gained what he wanted, he is left to eke out his days trying desperately to combat the unremitting sense of guilt that overpowers him and from which he can never escape. Therefore this is my best answer, as I don't actually think any of the themes are necessary "appealing" in a positive sense!