A subsection divides a section in smaller parts.
Pictures must be copied in each Chapter-XX/img folder and be prefixed with the chapter number to avoid collision on html output.
Then to insert an image, use the @figure macro with three arguments: caption, filename without extension and width expressed in centimeter:
@figure{Cuis, ch00-img1, 8}.
Figure 1.1: Cuis
In which file must be authored the solutions of the exercises?
Exercise 1.1: Solution of the exercises