No, I don't think you can do that. I think you can only place images in the vertex modeler. Here's a possible alternative. You'll need Illustrator or something else that can save a vector EPS file.

Open the image you were planning on placing into Carrara in Illustrator instead. Trace it there. Save it as an EPS and import that into the spline modeler. In the end you get the same results as you would have if you were moving spline points to match the image in Carrara.