Carousel with text using Matrix blocks
Old ticket, I know, but thought I'd answer.

Personally, I use a channel for carousel slides as clients for me have tended to mix and match them on multiple places on a site or stop using them then reusing them a few months later.

This way they have a pool of instances of reusable slides that won't disappear. Hopefully saving redoing work they've already done a few months prior.

If I've understood your question, I'd have a channel with two entry types. "Image slide" or "Text slide".

So when they add a new one they can choose if they want one with an image or just text.

Then depending on how you're constructing your pages you just need a Matrix component type that is named 'carousel' with an entries field with the slides channel selected as it's source or just an entries field on it's on in the page entry types you want this carousel to be. (I'd limit it to three or four for UX purposes).