Hi fellow May mommy. I saw your post on the May board. Have you lurked over here before? I just want to prepare you that these ladies are going to be honest and it might come off as rude but we're just trying to be honest. Basically, if you're already sure you are going to use the name it's a waste to post because we want to give feedback and honest opinions.
I don't care for it, our styles are just different. Shelton sounds like a surname, or a place name. I would probably assume boy before girl. It also sounds like Sheldon, which is definitely a boy name. Ashleigh is ok. Though I always wonder when people have a more contemporary and less standard spelling of a fairly time stamped name and say it's a family name. As in, a sister born in the 1980s? Because it doesn't sound like it would be Grandma Ashleigh and it's tradition to name after her. That doesn't mean there's anything wrong with using it even if that's the case, but I would use the phrase "honoring my sister (or whoever)" versus family name. To me, at least but I think a lot of others, that denotes a long standing family name that there is a long line of using. And all that to say, if it's not a true long standing family name, I would prefer to see the usual Ashley. And if you're only honoring one person versus many, there might be a better name out there.
What about swapping the order and using Shell as a middle name as well? Ashleigh Shell? Though I guess there's also a lot of "sh" sound going on. I went to school with a guy with the last name Shelley and everyone called him that instead of his first name. So I think it could still work to place Shell as a middle name and Shelly could be an endearing family nickname.
And if you really want the Shell connection as a first name, what about Rachelle? It's pronounced Ray-shell. The spelling is off, so if you really want to honor family I'd save it as a last resort.
Finally, you didn't say it, but I'm guessing Ashleigh is from your side as well? What about a name from your SO's side?