I too am new to having a shop but have a few thoughts that might help.
Since you have a lot of white and brown card items, I think your better pics are when they are against the opposite color for contrast. Placing your white based cards on a brown cardboard backdrop, and the brown based cards on a white backdrop.
Perhaps all with a slight tilt to show a slight angle, and include the contrast of the edge of your card against the backdrop. We all know it's likely to be rectangular, so cropping corners at a tilted angle is nice. You might want to choose a preferred tilt and keep all the single card images tilted the same direction for consistency. The multi tag images will break up any repetition.
You've got the idea here, but the image is blurry and the finger is distracting. Place the card flat and take a pic straight down? Less shadow since it's thin.
http://www.etsy.com/listing/160206775/happy-halloween-spider-web-card?ref=shop_home_activeHere you have the opposite color combination and it looks better.
http://www.etsy.com/listing/157448234/happy-40th-birthday-cake-card?ref=shop_home_activeHope it help! Best of luck with lots of future sales!