Custom icons and graphics for website

I would like to create some graphics for an existing website/web app. The graphics need to follow a certain general theme, but be colorful yet professional. The graphics include: - up to 5 different icons for various products/services - up to 3 "how-it-works" diagrams that will be about the size of a standard horizontal banner Samples/Examples may be provided to the designer, along with website colors, logo and size specifications. The designer should provide more than one theme (each theme would consist of a set of graphics as described above) - we will choose the theme that works best for us and may switch themes in the future. The designer should also be willing to make changes and corrections as requested before final delivery. The designer should be willing to provide the graphics in both complete format (.png/.jpeg/etc) as well as in editable format (.ai/.psd etc)