Fantastic! Did you designed them with a background or a specific task, or just letting your mind flow? because I like a lot the design of the upper-right bug, the one of the big legs and wondered how can be the habitat of such creature.
I had a specific task in mind, and that tall one with the long legs is a big part of the project. It is part of a contest at Conceptart.com to design a creature whose death is vital to the local ecology; it must die in order to allow others to survive. Here is the write-up I made for it (rough draft):
My working name for it is the "jellyback". It is a tall creature which feeds on the high fruits of trees. Once the creature reaches maturity it produces egg cysts within the large sac on its back. These eggs are very small, hard, and numerous. The timing of this is correlated with symbiotic flying creatures' breeding patterns. Once the flying creatures begin their courtship, the jellyback's vital energy is transferred to the sac containing the egg cysts. The sac then turns bright red, and the creature's limbs grow rigid as it dies standing tall. Once the jellybacks have died, the small symbiotic flying creatures tear into the sacs and feast on the mass stored therein. These nutrient-rich tissues and fluids give the flying creatures the energy they need to produce their young. The jelly-back's egg cysts are also consumed incidentally, but are not harmed by the flying creatures' digestive processes; in fact the process is essential to allow them to hatch. The egg cysts are later deposited by the flying creatures as they excrete them far and wide. The cysts then hatch and, using the nutrients from the flying creatures' droppings, begin the first stage in their life cycle. The dead jellybacks' bodies can remain fixed in a standing position for years, providing structures for the flying creatures to build safe nests high above the plains.