Your first question is hard to answer without some more details. E.g. which
pictures do and do not appear? What kind of files are using?
On question number 2, I would suggest to just put a link to the Gallery into
your existing homepage. You may have to put the Gallery in a separate
subdirectory since you want to refer to its index.htm file. Or you can just
link to that directory and the browser will default to the index.