Your graphics should be reproduced in the highest quality possible, but keep file sizes manageable particularly if the document is to be transmitted electronically. Ensure all graphics look consistent by standardising the title bars, using the same outline methods and keeping text-wrapping rules the same. Your document will appear piecemeal if some tables use shading, some pictures have borders and some diagrams use vivid colours.
Pictures, diagrams and tables are a great way to add interest to your proposals. They make your document easier to read and can highlight important points that might otherwise be buried in the text.