Android where to save images (private) ?? how to dynamically update images collection?

I am making a game in which I want user to give some featured items at run time from server. Currently I am saving images as Blob in sqlite db and that is really putting bad impact in overall performance.

If I write images on SD card then there are following possible two scenario开发者_Go百科s. 1) All mobiles do not have SD card 2) Any one can see/reuse/delete images

I don't want these things to happen. Is there any way that I can save images in drawable folder where no one except me can see images?