One other option was to look at adding in small images as links, is that what you're talking about?
Nope. I was saying that you could just add some CSS codes to Graphene's Custom CSS option or your child theme's
style.css to style the appearance of the shopping cart widget, without having to modify the code that generates the widget in the plugin.
*edit* I'm planning on purchasing the graphene mobile theme in the future, would you be able to suggest a good shopping cart plugin for that version? I haven't began the project but it would be nice to avoid that sidebar issue on a mobile screen.
Basically, there's no "sidebar issue" per se since the widget works - it just doesn't have that professional look you're looking for. This will be the same regardless of what theme you're using, since themes can't possibly style the content that is generated by all plugins that exist out there. You'll just have to apply the same additional CSS codes like you would in Graphene theme.
The Graphene Mobile theme has a Custom CSS feature as well. You can also use a child style.css file with Graphene Mobile, albeit in a slightly different way than you would on a normal desktop theme.