don't do these and you should be good.
the following are things that i hate. i hate these things because they look ugly or stupid.
of course, if you
know how to do these kinds of things
properly, then it's ok. most people don't know how to do it properly though.
[size=5.0x10^12pt]
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ PLEASE DO NOT DISREGARD THIS[/size]
striped wallpaper - striped wallpaper make the room look old and confined. lots of people also choose ugly colours. who has blue striped wallpaper??


dingy carpets - usually people build dark coloured or random coloured carpets, which make it look very old, worn out, and dirty

random assortment of windows - they make no sense, look bad, and obscure view

random "detail" window frame - they make no sense, and look bad

ramp pillars - make no sense, look bad

ramp walls - many people do this. it looks like crap. there is no real design to this, it's a load of random ramps put together and duplicated all over everywhere. it's a huge mess of bricks which is not pleasing to the eyes at all. please just never do this

feel free to disagree