Welcome to the forum rrkradio.
I have a few comments and suggestions but feel free to ignore any or all of them.
First, have a chat with your print shop about bleeds and how the cards will be printed and cut. Then make sure your document is set-up as the print shop suggests. This will make things much easier when you come to getting the cards - and the brochures - printed.
Next, following on from my first point, I would generally advise against putting a border on a business card (as can be seen on the front of your example). Unless the printing and cutting will be absolutely accurate (not impossible but may be expensive) you may find that part of the border is larger than other parts or it may even be crooked. If in doubt, don't line things up against the edge of the card as you can't be sure exactly where the finished edge will be. Even one millimetre can make a big difference on something as small as a business card.
My next suggestion would be to not obscure the image as much as you have done with the semi-transparent overlays. If you have a nice image then why not show it off?
Removing the overlays however would make the logo+text area difficult to see. What I would suggest in this case would be to isolate the logo+text onto its own "panel" either to the right, bottom or centre of the card. Fill this panel with a single colour and make sure the text has good contrast. (I've attached a very crude sample of the sort of thing but you don't need to go down the same lines.)
I like the choice of typeface(s) but I'm not sure about the use of old style numerics - the ones that drop below the baseline (3,4,5,etc). Old style numerics have their place, but for things like phone numbers they can be a bit distracting. It's a totally personal choice but if it was me I would look to see if the font included modern numerics also and use them instead. (I don't think Scribus caters for multiple numeric types so you may have to insert the characters manually, or maybe 1.5.x does things differently.)
On the back, there seems to be quite a large space to the left of the information. Left-aligning the top two lines of text in each block might look better (or it might not in the case of the second block down). Or, you could take the left-hand edge of each rectangle to the edge of the bleed, then stagger each rectangle down the card with each one getting larger. (Again, see my very crude attached example - I didn't bother using different colours or adding the text.) Notice that, in this case, if the cutting is a bit out it won't make too much difference.
I like your colour choices by the way. They go well with the subject matter and continue the theme from the logo.
In all I think you've made a great start but there are some issues - as I've mentioned above - that may need more thinking about.
Business cards are very difficult to get right. Such a small area to put over the right message. As I said at the start, please feel free to totally ignore anything or everything that I've said. Some of it - bleeds etc. - is important, while on the other hand, some of it is purely a personal preference. You need to go with what the customer wants and my opinions are no match to that.
Anyway, I hope I've been able to give you some reasonably sensible and useful advice. Please don't hesitate to ask for clarification on anything I've not explained well enough.
P.S. On the image you supplied the white border at the bottom-right is slightly thicker than the border at the top-right. I don't know if this is just an artefact of how your got the image but it does tie back in to what I was saying about bleeds.