On page load there will be s.t() server call ,on banner/image impressions there will be s.tl() server call so artificially it will depress bounce and bounce rate.

Here is the document that explains how each of these metrics works.

You can build a calculated metric using single access, but that will only work when looking at specific dimensions (pages, evars, etc.) and not from a site-wide perspective.  If you want something at the site level, then you can use single page visits.

You should use the metric that suits your need based on where/how they will use it in reporting.

Solution 1:

By the user of other metric we can solve this problem.

We can build a calculated metric using single access, but that will only work when looking at specific dimensions (pages, evars, etc.)

Single Page Visit / Entries

If you want something at the site level, then they can use single page visits.

Single Access / Visits

You should use the metric that suits the needs based on the requirement.

Solution 2:

Other solution to track banner ads is to populate the value of banner in local variable of javascript like banner1:banner2:banner3 and pass on that value to analytics variable like prop on page load. This can give insight that how many banner has been loaded at the time of page load.