Is there a way to customize the look and size of the alert modal? For example, change the frame, button look, fonts, etc..??

I imagine this likely requires a custom contraption. If so what's a good way about replicating the alert functionality so that it's more customizable? That's a long winded way of asking, how do I make custom pop ups?

In addition to Dialogizer, which offers blocking modal dialogs like a more general version of alert[], WigglyKit includes an example of a full-screen contraption which behaves like a non-blocking modal dialog; might be worth a look. While alert[] is not very visually customizable, it is worth noting that you can specify the first argument as rtext, which includes the possibility of specifying fonts, colors/patterns, and supplying inline images.