Heating your custom designed garage can be difficult to undertake, especially during the winter months. They usually don't have the same degree of insulation that your home does, which makes trapping natural warmth inside the walls a little harder to do. However, there are some options available to you that could be worth considering in the long run.
Propane space heaters
These are a brilliant way to heat a small space with little to no effort whatsoever. Unlike other liquid heaters, these emit no fumes or other byproducts – making them perfect for use in a smaller space like a shed. Furthermore, they're relatively inexpensive to purchase and can be moved around at will, which means you can bring them inside at the end of the night as well.
However, be wary of using them around flammable materials. While they aren't inherently incendiary, using common sense will help prevent accidents from occurring.
If your shed is a little larger than your typical installation or you use it as a commercial space, it could be worth investing in a wood barrel stove or other small fireplace. Taking the time to install the fireplace and chimney is a long term, permanent fixture and will provide you with a good source of heating all year round.
Not only that, but after installation they're a brilliantly economical way of heating a large floor space in a short amount of time, often burning for hours off just one or two logs at a time.
Infrared heat bulbs
Another option for smaller, residential sheds could be infrared heat bulbs. These are just like stock standard light bulbs except for the fact that they emit heat when turned on. If you're only warming up a small area, a couple of these lights could be perfect for what you're trying to achieve.