In the text box the Group Creator can explain how they envision the group being used and has the options of writing in Bold type or Italics. The text can be underlined or struck through.  Using multiple font sizes or type is not an option.

It is possible to cut and paste a URL such as this: http://www.cityofrochester.gov/article.aspx?id=8589936098 or there is also and Link option that lets you assign a link to a comments such as this one by highlighting the desired text and then clicking to Link icon to associate the selected text to the link you want it to actuate.

There is also the option of adding pictures such as this .jpg:

You can also add a .gif image such as this one of the Add an Image dialog box which I set this way for both images:

It can be an animated .gif:

You can also upload a file such as this one:
Block Clubs-9-26-2010.doc

In all cases you don't see the the final appearance of the images or posted file until you click Save .

The creator of the Group can go back and edit this text box as often a desired. While that repeated editing would permit using this text box as a database for accumulating documents such as meeting minutes, that may be better done with the use of the Discussion Topic portion of a Forum Discussion or with the use of Group Pages. That of course assume you chose to have a Discussion Forum when you set up your Group. Below is a .gif image of the Add a Group set-up-page Ima Tester filled out when setting up this group. Note the Features that were selected.
Ima's Add a Group.gif  One change since this ,gif was created is there is now an option to change the privacy setting of the group any time after creating it.
I don't see any way of customizing the appearance of the Group page the way it is possible for a member to customize their Profile page.

You can set up links in this text box to function like the tabs to organize what your group wants to present.

(Group TAB 1)    (Group TAB 2)    (Group TAB 3)