The right way to submit a design proposal is to use the design editor. It will provide you the information to follow the necessary steps so you can alter the original HTML template and CSS definitions to make the site look like you are proposing.
You can also add icons or custom images to make it match better your proposal.
phpclasses.org/design.html
Once you are done, click on the submit proposal link as soon as possible so you can get comments from the site users before the voting starts. After the voting starts you cannot make changes to your design.