Update README.md

Author: hellojavaer

README.md

@@ -6,7 +6,7 @@
 
 DDAL(Distributed Data Access Layer) is a simple solution to access database shard.
 
-<img src="https://github.com/hellojavaer/ddal/blob/master/doc/img/design_01.jpeg" width = "590" height = "390" alt="design" align=center />
+<img src="https://github.com/hellojavaer/ddal/blob/master/doc/img/design_02.jpeg" width = "590" height = "390" alt="design" align=center />
 
 ## License