What you put in a portfolio depends on the portfolios purpose. For example, if someone wanted to get a job designing environments for 3D games, then they might not put much in their portfolio showing vector graphic logos that they have designed. You can do it but, frankly, the hiring agency is not going to want to see that. If, on the other hand, someone is looking for an art director, then they might want to see how many different things you can do. In this case, a smattering of this and that would be called for.

If the idea behind the portfolio is to attract work, then you need to decide the kind of work you want to attract and display that in your portfolio. This goes beyond whether you want to do modeling and, therefore, display models in your portfolio. It may be that you want to get a job designing real-time 3D creatures. Then it would be good to have many of the images in your portfolio display a variety of 3D creatures created for real-time 3D content.

In other words, you need to think about what purpose the portfolio is going to serve and then design it, just as you would any piece of artwork, to fulfill that function.