Desktop PhotoApplet now supports transitions/effects in the slide-show and the interval is no more restricted to just 8 seconds. However, the maximum is 16 seconds and I think its enough. Also I will upload the .deb package in my first post and I'm sorry about one thing, it can't be installed in the device yet coz armel version I can't try. I guess it will be just scratchbox version for time being and hence it can mature. So, please, anyone willing to try give me some feedback. There is also option to choose not to have transition in the slide show.