I think senses and perceptions are an important part of species creation. How we sense and interpret the world around us is important. It extends beyond knowing what there is to sense. Our sense, compared to the senses of many animals, are very dull. We don't smell as well as a dog, we don't see as well as an eagle, and we don't have the extremely sensitive paws of raccoons. What we have is a more balanced sensory representation of the world.
But this means that there are a lot of things about the world around us that we're missing. We don't hear the sounds that a dog hears, and we're certainly not able to sniff out mold or follow a scent trail. That doesn't mean that other species can't, either. It is our environment which shapes our senses, and they evolve while we do. So, if a species evolved from, say, reptiles, their sense would more closely parallel that of their reptilian ancestors.
For instance, most reptiles don't rely on their eyesight, while some actually have very keen vision, others may only be able to detect variations in light and darkness. Others are totally blind. Snakes may have limited color vision, while other types of reptiles (turtles, lizards) are able to perceive a wider spectrum. And slit pupils can indicate a species that is active at night, while those with round pupils are generally active during the day.
All of these options and considerations revolve around just one sense, and one that isn't always dominant. Snakes have poor hearing because they do not have an external ear to amplify sound, but other reptiles have moderate or even good hearing. Snakes have excellent sense of smell, and a Jacobson organ which can convert tastes into smells. In addition, they have a sense we don't, special organs made to detect infrared radiation, allowing them to sense temperature differences as small as 2/1000 of a degree.
When creating a species with senses other than the ones we are familiar with, I like to consider how they process this information. Does their brain translate it into vision? Essentially giving them heat-vision? Or do they feel it along the surface of the organ? Constrictors (boas, pythons) tend to have these heat-sensing organs in their lips. What would it be like to be presented with a hot meal, if you had such organs?
How a creature processes this information is as important as them being able to sense it. Our brains interpret and filter all the information that our senses are capable of providing. Otherwise, we'd be overloaded, but this means that the brain is just as important a sense organ as our tongue, skin, eyes or ears. Our brains relate to us the information that it "considers" most important and that too is shaped by our evolution. If, for instance, one of our ancestors was hunting in the tall grass and their brain noticed movement that could be a attributed to a predator, the brain would put this information through immediately. However, if out of the corner of their eye they saw a rock that indicated nothing, the brain might filter out that information as 'unimportant.' It has nothing to do with what is happening, it poses no threat, why bother drawing attention to it?
So, consider a species' environment when you're creating. What preys on them? What do they prey on? What puts them in danger and what signs would they look for to give them warning? In addition to predators, consider weather conditions, environmental factors like poisonous substances, and the terrain. A species that evolved in a desert is more likely to be attuned to the movement of the wind than one that evolved in a dense forest.
Physical characteristics are also an indication of internal senses. For instance, because many reptiles--like snakes--don't have mobile eyelids, and instead have clear protective caps over their eyes, they have limited eye movement and tend not to rely on vision. Because they navigate by sound, bats have large outer ears, which take in vibration and amplify it. Outward physical characteristics don't exist in a vacuum. If you create a species with large ears or snake-like eyes, you also have to account for the change rendered upon their senses. And this works from the inside out as well. If you create a species which navigates by sound, large ears--or another such physical characteristic--are necessary.
What animal or theoretical senses most interest you? Would you rather be able to hear like a bat or sense heat like a snake?