Usurper has already covered a lot of this, but I want to touch on a couple of points.
Anything that uses the site's branding (which would include the name, logo, link, etc) has to be approved before it is made. I know this isn't how it has been in the past, but moving forward, ANYTHING from a t-shirt to a banner, to a business card that includes our branding must be approved.
In regard to a banner for the UK, the site is willing to pick up the cost for having a banner created (as long as the pricing is reasonable) to promote the site.
The things that should be included are:
The site name/logo (I can send this in vector format to anyone interested in creating a banner)
The site description: "Predator Prop and Costume Forum"
The site url: "www.thehunterslair.com"
If you want to add a Predator photo that is fine, but keep in mind that it will need to be limited colors as full color printing is extremely expensive and a full color photo would have to be 1) huge and 2) a GREAT photo to work well.
Things to avoid:
too many colors
putting a year on the banner (makes it obsolete in 12 months)
mottos, slogans, cheesy one-liners
I have to be honest... I am not very keen on the whole "clan" thing because it is already apparent you are from the UK and we aren't a costuming club like the 501st, so we don't really have clans in the same sense that they have garrisons. We are one big, happy family. Because of this, unless it is tastefully incorporated, I would avoid the Union Jack... you will already be displaying this in the UK, so it is a bit redundant.
Keep in mind, less is more... no, seriously, LESS IS MORE! Keep is simple, keep the text large and short so it can be seen from a long way away (our previous banners have suffered from text that is too small). Don't crowd the elements. Negative space is a good thing.
Anyway, there are my two cents. You guys are welcome to vote on designs if you would like, but keep in mind that we have to give final approval to maintain brand integrity and consistency.