Yes. If you have a knowledge of CSS and HTML you can easily get a fully customized Splash Portal!
It is possible to upload an additional CSS stylesheet to be loaded on all the Splash portals that can be managed by the system user.
You can use this stylesheet to enable some classes that can be used when you create the contents, specifying the list of classes to assign to a content block. Consider also that the Splash Portal is Based on Twitter Bootstrap framework, so you can use also the existing Bootstrap classes to shape your content.
For example, you can hide a content for a certain device resolution, such as mobile devices, just adding the class "hidden-phone" to the content.
As you can see in the example above, the text block containing the welcome message has been hidden for the mobile version of the Splash Portal.
You can also use the stylesheet to override some general classes used for the portal layout, such as page background, padding and margin options, etc..