Theme Horse

Hi Jelse

You can disable the logo options from dashboard-> apperance-> theme-options ->design-options-> custom-header

and select disable to deactivate the header logo.

If you want a big logo then you can add the banner for it. I Have seen already there is banner. we designed this theme in this way. So you need customization code for it.
To add header image

go to dashboard -> apperance-> Header

From here you can add the big image as a banner image.

Regards

Sunil