The Advanced Search layout has 1 dimension. And image is being responsive.
There are 2 ways to do what you want:
– add an image that has a bigger height, so that when the image resizes, it can still align with advanced search.
– or modify the layout of the advanced search for smaller screen resolutions.
There are many classes that you need to modify and some elements are found in other parts of the theme (as advanced search widget or shortcode) and the changes you make will affect all these locations.
Please try first option (it is the easiest).
And one last note: for image and revolution slider, on small screen resolutions the advanced search on map disappears. You will have to add also an Advanced Search Shortcode on the page, so that people can still use search.