can i sue if we didn't have a signed contract?

Yes.  First of all, although there was no handwritten signature, an email address or something similar on a writing will often be considered the equivalent of a signature.  Also, most contracts do not have to be in writing to be enforceable.  I see  nothing on the face of your agreement which would bar an enforceable oral agreement. You may have problems proving that you would have been able to sell the pictures for a definite amount of money, unless you already had a contract in place to do so. Also you have a duty to mitigate your damages.  You will have to show why you didn't mitigate by just hiring another model and do the shoot.  You could have limited your damages to just the $300  you advanced the model, plus anything extra you had to pay a replacement model.