A kitchen is not necessarily a place you may think of as cosy but as we often spend a lot of time our time in the kitchen and may eat the majority of meals in a kitchen / dinner, it is important that it feels relaxing and comfortable.
If you have a sperate seating area in your kitchen, simply adding cushions to the seats or a nice table cloth can add a touch of warmth to a room. You may also be surprised as to how much of an effect lighting can have. When cooking, you may want a reasonably bright white light but when sat dining you may prefer a warmer white.
It is important to think carefully about the practicality of any soft furnishings you add to a kitchen. Often a kitchen will get very humid and greasy and the grease / smells will stick to anything that is cloth. For this reason, you want the furnishings to be easily removable and washable. Curtains are often not a great idea in a kitchen but wipe down blinds can be used if you need that extra privacy. If you are struggling for natural light then as the kitchen has been converted out of a garage then why not install a skylight which will give the appearance of space.