Back when I was decorating cakes and when I was taking a culinary class on cake decoration, a real class, not 1 of the Wilton courses, the frosting was made with solid vegetable shortening.
Recipe - Classic White Frosting using Crisco
TIPS: make sure you use new, unopened crisco or other vegetable shortening. It develops an off taste that you can taste in the frosting if it's stored for long.
Instead of the milk to thin, and be careful not to use too much, use almond milk or even water. I always used about half of the liquid to thin some unless I was piping lettering, cornelli lace or string work, then I used the full amount.
Make sure the cake is totally cool. This frosting holds up to heat better than real buttercream, but it still melts.
I always stored the finished cakes in the refrigerator so the frosting and chocolate hold their shape.
DECORATIONS
I don't know where the pics are but hopefully I can explain.
Use a grass/hair tip, color some frosting grass green and use the candy corn pumpkins to make a pumpkin patch.
Smooth frost with orange colored frosting and use candy corn to make a jack-o-lantern face.
Frost using really dark blue or black frosting and place a white chocolate ghost standing up on the cupcake. Melt white chocolate, spread on parchment paper with a small offset spatula to about 1/4" thick. Place in refrigerator for 10 to 15 minutes to harden up some, then use a cookie cutter or freehand a ghost shape. Place back in refrigerator to harden. If it gets too hard, let the chocolate set out for a few minutes.
Frost with white frosting, leaving a moon like surface. Use milk or semisweet chocolate (milk for kids, semisweet or dark for adults) and do as above using a witch on a broom cookie cutter. Stand her up on the cupcake.
Frost dark blue or black as above. Make crescent moon and star shapes as above, except you can spread out to about 1/8" thick. Lay 1 moon shape and 3 stars on each cupcake.
Obviously, remelt the scrap chocolate pieces to make more shapes.
They make a lot more "candy corn" shapes now than when I was decorating cakes so you might not even have to mess with melting chocolate.
You could also pipe spiders using different sized round tips and make chocolate bats as above.
Oh, I have no idea of candy corn ingredients so check them out before you use.