I made a few tweaks per Jim's suggestion. I added some misty cloud coverage above the castle, and also added some cloud wisps above the mountains and on the right side. I also added a few more smaller birds meant to look like they were flying lower.

I also discovered that Mike Schley's Overland style already has cloud symbols, but I wasn't sure how they'd work semi-transparent. I added them as a base to the castle but most of the clouds are still from Forest Trails.

Also made a few other tweaks, like adding hills to separate the grasslands from the default terrain, and a few more trees below the castle peeking through the clouds.

I looked through my symbols to see if there were any other flying creatures, but couldn't find anything. Mike Schley's lovely dragons were sleeping, not flying. I even checked WikiMedia Commons to see if there was a flying pegasus or dragon in public domain that would be suitable, but didn't find anything. If anyone has any other recommendations for other flying symbols, please let me know.

I'm still practicing and experimenting with different maps of all sorts. Just for fun, I thought I would take a stab at designing a castle on a cloud. (Maybe it's a cloud giant's castle? Undecided.)

I started with an overland map set at 250 x 200, I believe. (Maybe I will do a city map of it later for a closer look, or perhaps a dungeon map.) I decided to use Mike Schley's Overland style. To create the clouds, I used various foams, rapids, and waterfall mist from Sue's Forest Trail set. It's hard to see until you move in, but there's a little bit of texture to the cloud added by the foaming rapids. I put them on a new sheet that I called "Clouds," placing it below the Roads sheet, which was the lowest of all of the surface-level sheets. I tried to put a drop shadow on the Clouds sheet but couldn't get it to work (entirely possible that some or all of my cloud ended up on the wrong sheet). Instead, I drew inspiration from the manual cliffs shadows that Sue had in Forest Trails. I used the Sea Contours to draw a shadow, and then moved the "Contours (Sea)" sheet to render before the cloud.

The castle, with its extra towers, was added to a "Symbols on Cloud" sheet that I created. I also had a Flying Lowest and Flying Low sheet above the Cloud sheet, and Flying and Flying Highest sheets below it. I thought the four different flying sheets would allow me to show things at different altitudes with different drop shadows, but I ended up only using one of them for the birds (maybe Giant Eagles or Giant Hawks?), which from the cartouches from Forest Trails.

Anyway, there's my first pass at something I haven't see here before.