To give your guest room an Irish influence, you might immediately tell yourself that you need to find shamrock drapes, and kelly green pillowcases. In reality, Irish design is about incorporating comfort, deep colors, and soft lighting. Think Irish pub rather than Saint Patrick's day.
Keep your guest room mostly neutral with deep browns and rough woods. If you want to add green to your Irish-inspired space, use deep shades that will compliment neutral walls. Add color in the bedding and accessories like lampshades and picture frames.
Changing up the lighting in your guest room is one of the most important keys to making it feel like a pub in Ireland. Avoid overhead lighting unless it is on a dimmer switch. Instead, try using dimly-lit table lamps, torch lamps, or even flickering candlelight if possible. Candles in neutral colors provide the softest, most natural lighting, and will give your guests a romantic atmosphere.
To punch up the Irish factor, add artwork portraying flags, photos, or family crests that represent Ireland. A map of the country itself in black and white or sepia can be a large, high-impact art piece. A rough, wooden trunk at the foot of the bed is functional to hold blankets, and gives the feel of a rustic bar in Ireland.