These cards are lovely! They are created by Jessica Nielsen, a Dutch designer who makes bright and fun illustratrions. Next to that she also develops her own colourful paper and textile products, such as bags and pillows.
All of these are for sale on her own website. But you can also find her cards at Huiszwaluw, a lovely shop in Ghent. Attention: at October 29 the shop is moving to Hoogpoort 3B. Just so you know :)