I know I'll regret getting in the scrum, but, @mhikl, two things:
- If you are using an i-anything, and viewing the epub in iBooks, there's nearly always a problem with centering, FWIW, and,
- In case that isn't it, although I want to whip myself with a wet CSS guide for saying this, insert your image, in BV, and then {sigh}, put your cursor to the left, LEFT of your image, and THEN hit the center text icon.
And to learn how to get around the dreaded Jobsian i-Anything centering problem, if #2 doesn't work, you'll have to break down and learn CSS. It's not that hard, but the cascading part can bite you in the a$$.
Lastly: despite Valloric's Herculean efforts, no matter what anyone tells you, Sigil isn't a "WYSIWYG" editor for epubs. It really isn't. There ain't no such thing, although you might want to try Jutoh (Hitch
slaps self in head). It's not elegant, and it's not very...well, techie...but if you can write a little html, you can make decent books with Jutoh. Not great; not elegant; but serviceable. And you don't need to know a word of CSS--so to speak. Jutoh might be a better match for you at this stage...not to dissuade you or encourage you NOT to learn the good meaty stuff, but if you want to make it NOW, that might be a better way to go, today. Just a thought.
HTH,
Hitch