After deleting/adding some png files to project, i have got messages when building project.
\"file ProjectPath\\aaa\\xxx.png is missing from working copy.\"
This is occurred when you delete file on Xcode, but didnt tell svn server about it.
Go to command line tool, and delete file directly.
svn delete missingFile.m
and commit it
svn commit -m "Deleting file"
note that if you delete .svn folder, the warning is disappear but you will lost communication with svn server.