Before you start selecting orchids just because they're pretty, figure out what your actual conditions in regards to light, temperature, and most importantly water are going to be. You can achieve a large light gradient that will allow you to keep orchids with widely different light requirements, and normal room temps suit a wide variety of orchids. But all of the plants are going to be subject to the same watering regimen, so it behooves you to nail down what that regimen will be before making your selections. For example, my Dendrobium loddigesii forms a lovely mat of canes and leaves pretty quickly, but if it gets watered and fertilized year round it won't bloom. Haraella odorata would love a constant flow of moisture through the substrate, but Schoenorchis fragrans will rot in short order with the same regimen. Do you have a particular plant in mind? If so, figure out what it needs, provide it, and choose companions partly for their liking the same conditions.