What are some good ideas for a finish on a concrete slab?

It depends upon what you want to accomplish. Is this for a finished room or just a garage? How much money and time do you want to spend on this project? Do you just want to paint it or seal it? As you can see, more information would be helpful.

Homedepot has a variety of paint. Some are colored, and some have sparkles. If you do this indoors mark sure your well ventilated. If it's for outdoor you'll be ok. Our can roll this on with a roller with a stick handle

You could paint a “carpet” onto the surface with a couple of colours of concrete paint and some painters tape or a stencil