Even if you won't localize your site immediately, build localization into your design specs. For instance, it's less expensive to translate HTML text than to change graphics. Saving graphics as layered files with the text on a separate layer makes them easier to alter, as does placing text under graphics rather than on the graphic. All languages are not created equal. Think how this might affect page layout.
Flexible designs work best.
Be aware of cultural differences. An icon of an octagonal U.S. stop sign has no meaning in many parts of the world. Present a clear choice. On the Web, communities are identified by language, not countries, unless the site is truly localized for a particular country. If it's not, using a flag to indicate a language can be confusing.