If you’re freelance and there’s no contract, you own the design rights. You should be signing and dating your designs.
How do I know this for sure? I did a small project for a UK client without a contract. The designs were knocked off by a market competitor so they took them to court - in order to do this they asked me to sign paperwork passing the design rights for this shoe over to them, which I willingly did.
But yeah, try to get it in a contract and I will try to practise what I preach! And when I do use my contract - I get the client to agree to whether I can use their work in my portfolio, post it online, and when I can do this (say when the product is at retail).
The above client works in a very competitive marketplace (hence the court case) and we have an agreement that I don’t disclose the work, nor that I work for them.