Are graphics headers important?

Hi all!

I just started with Groupsite a week ago, with a couple of hobby groups. Almost the first thing I did for both of them was to put together the header graphics, which, to me, are important as a "first impressions" thing. 

Once I'd settled in, I decided to have a look at other groups that I may be interested in, and saw that only a few of them had set up any header graphics. So now I'm wondering if neat graphics are necessary to pull in new members?

I'd appreciate any thoughts on this, and for those interested, my groups are:-

The Game Cafe and PSP Graphics.