Can I rename the header labels for an table?

I’m attempting to create a table from an aggregate model, but the column headers are not looking very friendly. Can I change these?

Yes. This is possible in any Skuid page. In the page builder, click on the field in the table/editor you want to rename and then enter a new Custom Label:

Anna is correct, fields in Tables / Field Editors always allow you to specify a Custom Label, regardless of whether the Model is Aggregate or regular.