Okay, so I have taken the time to put up a little guide for you all about canine communication. This could help in fanarts, fanfictions, in real life with dogs or is just handy to know.
The Happy Dog: Generally, a happy dog will have relaxed ears (usually pushed back in a relaxed way), a low, relaxed, wagging tail and an overall relaxed expression and stance. This dog knows that all is well and good and that he can just relax and have a good time. A happy dog is quiet. Some dogs that have grown up around people will learn to copy a human smile by drawing back their lips and exposing their teeth and tongue. They will still have the same relaxed tail, stance and expression.
A submissive dog is almost always a happy one. Dogs that know that humans are of a higher rank than themselves will not feel pressured to take charge of a pack of humans.
Submissive Gestures: Ears back, low tail, expose stomach, avoid eye contact.
The Aggressive Dog: In the canine world, there are two types of aggression; fear aggression and dominance aggression. In both cases, this dog will bite you if he/she sees need.
Fear: A fearful dog is most likely very confused. Usually seen in dogs that have been or are mistreated. This dog would have it's tail tucked as far as possible between it's legs, it's ears pushed back as far as possible, will be cowering but may be snarling, growling and baring it's teeth. This is the most dangerous kind of dog to be near. May bark.
Dominance: A dominant, aggressive dog will stand tall, it's ears erect (or as 'straight up' as possible), it's tail high and stiff. Will usually bark and/or growl. May snarl and bare it's teeth. This dog's owner's are probably not firm in training with it, or have trained it as a guard dog.
Other Gestures: These are other gestures that do not fit particularly under any of the above categories. *clears throat*
Play Bow: If a dog leans forward so that it's chest and forelegs are almost flat on the ground, but it's hindquarters are high in the air (usually accompanied by a high, quickly wagging tail) then there is no question about it--- This doggy wants play!
Excessive Scratching/Licking: Definitely a nervous dog. Usually seen in dogs that have been in excessive 'trick training' or something of the like. If this dog has been shaking hands for the last half our with only "good dog" as a reward, he will probably get nervous and display either scratching, licking or another nervous habit to try to relieve stress.
Well, the I have covered most of the basic expressions of dogs. This is stuff I have picked up from reading a book called
The Secret Life of Dogs (I forget the name of the author) and also from this site
http://www.dogbreedinfo.com/ which I strongly suggest you visit. Feel free to ask questions and I will do my best to answer them.