You can chose any banner and link it into your shop. Just copy the link and then put it into the shop description which is in the create/edit a shop.
<center><a href="http://www.neopets.com/guilds/guild.phtml?oid=superbabyq"><img src="https://www.angelfire.com/ultra/dream23/usul.gif"></a></center>
<center><a href="http://www.neopets.com/guilds/guild.phtml?oid=superbabyq"><img src="https://www.angelfire.com/ultra/dream23/meerca.gif"></a></center>
<center><a href="http://www.neopets.com/guilds/guild.phtml?oid=superbabyq"><img src="https://www.angelfire.com/ultra/dream23/kougra.gif"></a></center>
<center><a href="http://www.neopets.com/guilds/guild.phtml?oid=superbabyq"><img src="https://www.angelfire.com/ultra/dream23/bruce.gif"></a></center>
<center><a href="http://www.neopets.com/guilds/guild.phtml?oid=superbabyq"><img src="https://www.angelfire.com/ultra/dream23/kacheek.gif"></a></center>
<center><a href="http://www.neopets.com/guilds/guild.phtml?oid=superbabyq"><img src="https://www.angelfire.com/ultra/dream23/down.gif"></a></center>
<center><a href="http://www.neopets.com/guilds/guild.phtml?oid=superbabyq"><img src="https://www.angelfire.com/ultra/dream23/blue.gif"></a></center>
<center><a href="http://www.neopets.com/guilds/guild.phtml?oid=superbabyq"><img src="https://www.angelfire.com/ultra/dream23/rainbow.gif"></a></center>