I would go easy on mixing patterns in a kitchen. You can mix them but make sure the colors are complimentary and that the patterns don't fight each other. In other words, the patterns should be of similar style. Don't use too many busy patterns. If possible, make sure the patterns are far apart from each other.
The important thing to remember is to choose patterns that are not too similar, but that have similar colors. Example: a floral pattern with earthtones combined with a striped pattern containing 2 or more colors within the floral pattern will work fine. Look for patterns within patterns. (A scroll that's black paired with a black stripe or other shape)
Keep colors in the same family OR in your chosen complimentary color. One pattern may be busy (such as floral) while the other should be on a small scale (such as a check or plaid). Patterns need to be different scales with similar colors to work well together.