The SFTP connections provided by PowerCenter can only be used for the standard source / target flat files, not for binary files.

Having written that, you can always write your own Java code in a Java Transformation to perform a SFTP transfer for any file accessible locally. I've done something similar years ago with FTPS, that works. You just need to find some JAR library which provides SFTP functionality which you can use without violating any license rules; that can become a real challenge for commercial use.

Regards,

Nico