For your Logo, your best dimensions will vary depending on your design theme. However, we have some suggestions to help ensure your logo will look great on your first try.
-Always try to upload your logo in as high a resolution as you have
-Make sure your logo is on a transparent background
-Ensure your logo fills up most of the image's area. (Not a lot of blank space around the edges)
-Generally, a horizontal logo (wider than it is tall) will look better than a vertical logo (taller than it is wide).
Here our logo satisfies many of the recommended logo requirements.