Unfortunately, you can't use wall tiles on floors. They are weaker than floor tiles, and won't be able to withstand the foot traffic without cracking. You can, however, use floor tiles on walls.
To understand a little bit more about which types of tiles you can and can't use for certain applications, it is important to first understand how tiles are classified. All tiles are graded on a scale that ranges from 1 through 3. Typically, the grade for a particular tile is printed on the box that the tile comes in. 
Grade 1 tiles are the strongest and are suitable for heavy-duty use such as on high traffic floors. They can, however, also be used on walls. Grade two tiles are similar in strength to Grade 1 tiles, but may have slight imperfections. Again, these tiles are suitable for use on both floors and walls. Grade 3 tiles, on the other hand, are far thinner and lower quality than the other two types of tiles. These tiles are only suitable for walls and should not be used on floors. 
Glazed tiles also have a wear rating provided by the Porcelain Enamel Institute (PEI). Tiles with a rating of PEI 1 and II are not suitable for use on floors. PEI III tiles are moderately strong and can be used in all residential applications. PEI IV tiles offer high wear resistance, and can be used in residential and light commercial applications. Ratings over PEI IV are extremely durable and can withstand heavy commercial use. 
As long as your tiles are Grade 1 or 2 and have a PEI rating or III or higher, you can use them on the floor. Otherwise they should be reserved just for use on walls.
This video shows some of the primary differences between floor and wall tiles, which may help you identify which type of tile you have: