Fitting ethics into Wittgenstein's logical philosophy

I've been thinking about how ethics and aesthetics fit (or don't fit) into Wittengenstein's philosophy, especially since we ended class last Wednesday by briefly opening up this topic. It seems that, according to Wittgenstein, ethics cannot be discussed philosophically. I suppose this is because ethical propositions and statements of judgment have no place in Wittgenstein's analysis of language as made up of logical propositions that can be confirmed as true or false when compared with reality.

But I feel that ethical propositions could be meaningful, and can have a place in philosophical discussion, if we consider them as referring to abstract concepts that are for the most part universally understood. I'll attempt to explain what I'm trying to get at (and maybe if I can't I'm just demonstrating that Wittgenstein was actually correct in denying the possibility of discussing such matters) :

The language we use to discuss ethics and aesthetics refers to a concept, a notion that has no physical reality. Just because it isn't a concrete object doesn't exclude it from reality (and I think Wittgenstein would agree that not all logical propositions have to refer to concrete objects in reality). In this way, such a statement as "murder is wrong" has meaning and can even be deemed true as long as there is a understanding of what one means when one uses the word "wrong."

If Wittgenstein excludes aesthetic and ethical propositions, then it seems he must also exclude emotional propositions--which I suppose may fall under the aesthetics category. Thus such statements as "I am happy" would have no meaning. But clearly emotions are part of reality, it's just that their meaning, what they refer to, is harder to pick out.

To get back to the assertion that ethical propositions can be discussed, we should consider what Ishiguro says on Wittgenstein:

...his belief in the inseparability of the grasp of the public, conventional use of signs and their meaning or reference, and in the equally intimate connection between the understanding of what a proposition says, which is the understanding of what will be the case if the proposition is true, and the kind of objects the proposition is about (43-42).

I guess what I'm trying to get at is that Wittgenstein clearly believes that the meaning of signs (i.e. words in language) depends on the way people understand and use them--and it seems to me that people use and understand such words as beauty, and right and wrong with an understanding of what concept they're referring to when using them, even if this concept has no reality separate from that which is in the minds and bodies of language-speakers.