Answer
For a static image stored on disk, resizing the containing cell in the designer does resize the image proportionally, preserving its aspect ratio, and this is visible directly at design time. For a dynamic image fetched from the database at runtime via a bound SQL query, though, only a placeholder is present at design time — there's no way for the report to know in advance what size you actually want that specific runtime image rendered at, so it falls back to rendering the image at its literal stored pixel size in the database rather than any size configured in the layout. In practice, this means the images stored in the database need to already be sized correctly for how they should appear in the final printed/PDF output, since Report Designer won't scale them down or up automatically at runtime the way it does for static design-time images.