I've made hundreds of actual moss baskets with students and many have trouble with the concept that for moss hanging baskets, you plant the trailing plants on the sides and the top, and the plants which grow upright (geraniums) on the sides and the bottom. This means your basket will grow so that the trailing plants grow through the upright plants and make a full, rounded floral display. The mistake many people want to make is to plant the trailing plants on the bottom and the upright plants on the top, where they just grow in opposite directions to give you a long, columnar basket.
When you arrange your miniature hanging baskets, try to put some 'bushy' miniature plants on the sides and towards the bottom of your basket, and set the trailing miniature plants so that they weave through these plants on their way to hang off the base of the basket.
You can use bits of railway scatter, dried bits of acrylic paint, or colored bits of sponge to represent plants in smaller scales if you wish. You can find kits for plants in dolls house scales of 1:48 to 1:6 or make your own plants to fit into your baskets. You can also cut interesting bits of dried or silk plant material to make plants for your baskets. Try making baskets for Autumn, Winter, or Spring scenes as well as traditional summer baskets with geraniums and petunias. Have fun!