There is one hard and fast rule. Keep your visitors interested or they will leave in less that two seconds. Give them information, give it to them quickly, make it easy for them to get around your site and don't add graphics that serve no useful purpose. Beyond that, just about anything goes. The look and feel of a site has everything to do with its structure and its content and design.
Good sites have a consistent graphic style and strike a balance between design and content.
Limiting a users choices can be boring, unless the experience they are offered is a form of training or a learning experience. Scale and proportion matter. Elaborate graphics or large photographs should not overpower the words on a site, unless the point of the site is to promote graphics or photographic services. The design approach should support the intended function of the site and the features and elements that are contained should have functional purposes. There is a lot to consider here.