Yes. Set the Pages menu to the first page only, and the converter returns a single BMP instead of one image per page. Choose 72 or 150 DPI if the image is meant as a small thumbnail.
Image formats such as PNG and JPG are made of pixels, so zooming in past their resolution shows the pixels. For sharper pages choose 300 DPI, the highest setting, or convert the PDF to SVG, which keeps text and vector drawings sharp at any zoom level.