So so many forums I visit simply have the default style for their software, or have bought one from a reputable company and not customized it in any way. At least change your logo, then you have a brand image. (which is important). Some good examples of customization for each of the major commercial forum software are : http://www.offtheme.com/forums/ - for IP.Board http://www.parlancia.com/forums - for vBulletin http://xenfans.com - for XenForo These may not be the best examples, but they're the best I personally can see in my little search of the web. The customization of your site, the skin, and even something as small and ridiculous as the smilies all makes the site 'stick' in the visitors mind. I know I personally am more inclined to join a forum which has a nice custom skin, rather than a site which does not.
XenFans is a terrible example, the only thing that's really different is the logo and the reverse gradient at the top.
I agree a custom style can help, but I wouldnt say its needed. You can make due for awhile on default styles with your own logo. You just have to pick non eye killing colors. Specially if your going to get your own skin. Nothing turns members away more than blinding weird designs and colors. I would highly suggest to ask your members about your layout and colors. Try to get them all to participate and vote. Maybe even offer a contest for logos and such.
they also have lots of subtle changes which LOOK default Such as the glass type outlines on either side, and the winter type background..
A custom style is very expensive though. If you want something then $500 is the cheapest you will get, but you could pay much more. A logo and nice free/prepaid/club theme is all you need at first
Not a proper custom design, if so can you please provide me a link to their websites? I don't mean just changing the colours about or adding a logo - I mean developing a theme from scratch in photoshop, showing the client, getting changes made and then coding and testing.
Oh, with PSDs and such it's gonna be more. These people are doing it for ~$110: http://nanoskinners.com/services.php?service=custom_theme