Can you paint a room using different types of paint (eggshell, flat, or semi-gloss)?

I just finished painting a room Irish Cream in eggshell and I also did the trim in a nice off-white eggshell color. I wouldn't have chosen eggshell if it wasn't for the fact the wall has vertical boards every two inches. So I have this New England Cupboard that I wish to paint a darker brown but possibly a flat or semi-gloss. All I care about is making my living room look like one of those in the fancy magazines without having to go out and buy one. So is it better to keep with the pattern of eggshell or do the more modern thing and switch off?