Here's a picture of some ticks
http://www.lymenet.org/picture3.shtml
They can be different colors, some have a white spot on their back. Some are larger while some are very small.
Usually if you find them in the house it's because either you've carried them in or your dog has. If they have been attached they'll have blood in them. If they haven't been attached you cannot get any diseases from them!!
We live in a wooded area and deal with ticks all the time. We've had several already this year on the dog and on us, but we've NEVER had any problems from a tick (ever).