The news items are titled automatically from the email subject line, so it would help if you can make this informative - and if you intend to send items regularly in one month, a date in the subject line in ISO format is a help : i.e. 2006-04-20. Such dates have the advantage that they then automatically sort and display in date order.
Any textual info should be as plain text or html, so it is searchable, not in graphical format. There is no problem with it being in nice fonts/colours, and laid out in a tidy display format, see many examples on the news pages.
Please do not attach .jpg graphic to your email, they are a lot of work to process, to display on the web, (I have to create a web page to contain them), and usually take up a lot of web space unless I also re-size them.
If you want to include huge posters, flyers, etc., find somewhere on the web that you can upload them to, and then just put a pointer to this location in the email. This way people have a choice as to whether to download them or not, and they then cause me no extra problems. See the separate news item on how to do this.
If you have a lot of events for the calendar, send a separate email, see the news item on recommended formats.