Here is the chalk drawing I made for the GalaCon 2019, with the assistance of other bronies who helped me to fill in the outlines for this drawing.  
The idea was of course to honor the guests of honor Andrea Libman (voicing Pinkie Pie and Fluttershy) and Tabitha St. Germain (voicing Rarity).  
With the many predictions of intense rain I made a draft of how I think these three charakters might react to impending rainfall. While Rarity would probably levitate an umbrella and be actually concerned about the rain messing up her mane and tail, Pinkie would probably not really care and wear her umbrella hat (from the episode “Feeling Pinkie keen”) more for the fun of it. While Fluttershy would probably have learned from the ducks and other animals to see the pleasant side of a rainfall, go with it and fix her mane later on if necessary.  
Since the rain was really about to fall at the time this picture was taken I didn’t quite complete it.  
The characters are missing their nostrils, I didn’t add some shading I would have added but for the impending rainfall and I would have worked out Rarity’s mouth (with gritted teeth) more. I think I set Fluttershy’s wings a bit too high and parts of Pinkie Pie’s rear had not yet been filled in (plus the lack of her tail). Other than that I am quite happy with how it turned out given the time pressure to get it covered before the rain set in.  
Shortly after the picture was taken the drawing was covered by the foils brought along by Themisto97 .  
Thanks a lot for taking those foils along, Themisto. They saved the chalk drawings made on Friday and thereby made a really great difference at the GalaCon :)