Can I add my own 'signature' every time?

This may seem like a foolish question, but would it be okay for me to put a little link and banner image at the end of any post I write on the forums, until the built-in signatures function comes online, or would the be frowned upon as against the codes of conduct?

I would say it's best not to, particularly if it's advertising a personal project such as a blog or a business. We'll have signatures back eventually, and when they come online, you'd then have double images you can't edit on each post.