You can brighten up your emails with the use Outlook Express Stationery. This usually consists of a background image, and formatted font. It's very easy to add Stationery to your emails. Try the following.

NOTE: If you use Rich Text, it means your emails will be sent using HTML. This means you can do all the fancy formatting you want (bulltes, italics, Bold, etc). However, a lot of people don't like to receive emails that have been formatted using HTML, because there are some security issues involved. For example, some dangerous JavaScript can be executed in the background, if you receive HTML emails. If you use Plain Text, then potential for harm is greatly reduced. You can't do any text formatting, though. To change an email into Plain text, simply select it from the Format menu.)

You should get the following dialogue box popping up:

You can select one of the inbuilt templates. Tick the box "Show preview" to see what your email will look like. If you like any of these, click OK. Your new message will then have a background image.
If you don't like any of these (and you won't!) then you can create your own stationery in Outlook Express. To see how to do just that, move on to the next part.