I wouldn't go down the route of asking Google to index them as such.

I would just get the pages you want indexing more noticeable by posting them on your Google + page, twitter, Facebook etc.. Always works for me.

Also try www.pingomatic.com works well.

I would say it comes down to page loading speed and user engagement. If the page is taking a lot longer (which your website doesn't) to load then this could influence the ranking. Again if users arent engaging well with your page and the bounce rate is high then this could influence the ranking as Google may see your page as not being the best match to their search.

I don't think the size of the image or the style of your page is going to influence the ranking of your page/website. The only case I can see this being so is when it affects the users experience.

Yeah you could either do a 301 redirect or just set the canonical tag in your page.