The next aspect to consider is the technical development of your site. If it is going to carry heavy duty pictures then you will need to design the site in such a way that it loads quickly. People have a very short attention span and if something is not in front of them instantly, they are bound to leave it and move on. You will also need to ascertain the storage space you will need online for all your data and tweak your web package accordingly.
When you are actually designing your site, you have to pay attention to accessibility. Depending on what it is that your site is promoting, you have to be sure that everything your readers need is available sequentially on the site. This means that the font you use, the color of the buttons and even their placement is very important. What you could do here is have a dummy site set up which only you or the designers could have access to. You can keep testing this site online to figure out how it works and how to improve on it before you actually release it online.
Make sure that your site is designed from the user's perspective. Imagine yourself using the site and design accordingly. It may not live up to your expectation aesthetically, but it will make a world of difference to how your site is received. Pay attention to how you create the path of navigation on your site. One has to flow smoothly to another and all relevant buttons should be available on every page to ensure that the person can go to where he requires from any given point. It takes a while to bring aesthetics and user friendliness together.