What are the image creation flags?

You seem to be mixing images with pixmaps.
If you want to create a pixmap with format PF_BGR888 then
either use createpixmap or convertpixmap.
All pixmaps are 'dynamic' in that you can change them at a pixel level.
To then load this pixmap into an image use
loadimage(mypixmap,DYNAMICIMAGE) or the other flags documented under Loadimage.