Something is blank if there is nothing on it yet. Things that are usually described as blank when they are new are pieces of paper, an artist's canvas, or a computer storage device like a hard disk. These are all things that are blank before you write on them.
A group of things are concentric if they all have the same center. The circles in the picture all have the same central point. Any shape can be concentric - triangles, squares, or even three dimensional shapes like spheres.
Something is spotted if it has a pattern of small, round things all over it. Many animals are spotted. If the spots are perfectly round and even they are usually called dots. People will usually call animals covered in dots spotted and clothes covered in spots to be dotted.
Floral is the name for a pattern, usually used on fabric, that is made up of pictures of flowers. Floral prints are very popular on skirts, dresses and on loungeroom furniture.