You can disable the text-wrapping around the chapter pictures by changing the first lines of the OEBPS/css/style.css file that you can find inside the epub (edit with Sigil, or with any text editor after extracting from the epub, which is just a renamed zip):
Code:
/* Wrap text around chapter titles: */
@import url("wrap.css");
/* Do not wrap text around chapter titles: */
/* @import url("nowrap.css"); */
Simply comment out (or delete the) "wrap.css" line and uncomment the "nowrap.css" line, i.e., make it look like this:
Code:
/* Wrap text around chapter titles: */
/* @import url("wrap.css"); */
/* Do not wrap text around chapter titles: */
@import url("nowrap.css");
If you want to remove those images completely, add "display: none;" to the div.chapter-head block in the same file.