Your Logo Matters!
A logo sends a crucial 1st impression to potential buyers so it's very important that you have a solid looking logo. If it looks home made, it will hurt your sales. Some things to avoid:

• flaming logos
• spinning logos
• out of scale logos - too big or too small for the template you are using
• bad color combinations that clash with your template 
• hard to read fonts or font sizes that make the logo text hard to read
• too much information -  it has to be simple and direct with a minimum amount of text 

A logo needs to be iconic and instantly recognizable even at small sizes. Ideally, it should not contain any text other that your store name. Think Coca Cola, IBM, Apple, CNN, etc. Simple and direct...

If you have a great logo then stick with it but if your logo is not conveying the image you want, consider creating a more professional one - see http://myshopkart.net/faq.php#64