Another fan of the sketch challenge here. And I'd have to say that originally I found it very hard, because it's not how I naturally work with putting a card together, and for the first couple of months it really was a challenge! But now really enjoy following them. Some are more complex, but some are very simple and graphic, so that really just a couple of nice papers and the stamped image are all you need. This week's one, for example, didn't really need any fancying up. That was SC233, and SC229, 228 and 227 all look as if they must have been strong simple sketches. I've certainly ended up with simple cards based on them.
The cards you have with the ovals, there's not a lot I can think of to change them up and keep a smiliar layout. But the Father's Day ones, even something like trimming another 1/4" off the base layer and cutting it into quarters, so that there's a little gap between each quarter, would add some extra visual interest. You might have to move the ribbon down a little for it to work, but you could experiment. A bit like this -
IC180 Eva Inspired by Cook22 at Splitcoaststampers.