There are multiple types of indoor units available to serve your home's needs.
There are the standard wall mount units, there are recessed ceiling cassette units, and there are concealed duct units.
The indoor unit(s) you choose should be based on your home's layout as well as your aesthetic preference.
Wall Mounted Indoor Units
The most common of mini-split indoor units, wall-mounted evaporators are the cheapest, easiest to install, and often most efficient option available. Because of their popularity and volume, they are available in the greatest variety of sizes, types, and efficiency. They are also usually the least expensive indoor unit for most applications.
Wall mounted units are typically installed near the ceiling on an exterior wall. They require approximately a 3" penetration through the wall to connect the refrigerant lines, drain tube, and connecting wire. The wall must be vertical, and the unit must be mounted level. Wall units are typically 30" - 42" wide, 12" tall, and 6"-10" deep. Rooms with narrow walls, high windows, or other obstacles may require a different type of unit.
A suitable wall unit can be found for almost any application. They range in size from 6,000 BTU/hr all the way up to 36,000 BTU/hr, and are available for both single-zone and multi-zone systems. They can also be used in both cooling only and heat pump mini splits, and models designed for use in low temperatures are available as well. Some manufacturers, such as LG, even offer wall-mounted units with higher end finishes and discrete designs to better fit with your home's decor.
Wall mounted units offer the best combination of value, efficiency, and flexibility for most applications.