In How to: Create a Multi-Column Report
is described how to achieve the layout. In general, Report Header/Footer sections, Group Header/Footer sections and the Detail section span the width of the column, so the list of items should be rendered into one of these sections. And as you want to put a PictureBox with the full-width size of the report itself, it can be placed into Page header section which spans the actual width of the page, not the width of the column.
If this doesn't work for your scenario we would need to investigate the report definition that you have and also what exactly you are trying to achieve.
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