Hm...
Problem is a lot of the main event or upper-carders have already worked together at one point or another...
Randy Orton (heel) versus Sheamus (babyface) - It's been a while since these two tangled, and the Big Show throwaway feud could easily turn into this.
Antonio Cesaro & Wade Barrett (heel) versus Kane & Daniel Bryan (babyface) - I'd hoped that the tag titles would drop to Ziggler & Langston at Wrestlemania (even moreso after they teased a continuation of the Shield feud), but what happened happened. Still, I think these two could do a great job as a duo, with Barrett carrying the promos and Cesaro the matches. Of course, Barrett is a mid-card champ...
Kofi Kingston (babyface) versus Bray Wyatt (heel) - I really think this could be a good feud for both men. Wyatt's character and promo could hopefully bring out a stronger edge to Kingston's character and attitude, one we've only seen glimpses of in previous years. I don't rate Wyatt as a future main eventers, but he's defintely going to be a top feature in the mid-card if treated right.
Wade Barrett (heel) versus Christian (babyface) - I don't think these men have ever really worked against each other, and I'd love to see Christian put over Barrett in a good feud (someone has to, considering how much they love stopping his pushes). I'd hoped for a feud with Jericho ending at Mania since he was his NXT mentor, but this would suffice.
The Miz & Zack Ryder (babyface) versus Rhodes Scholars (heel) - Shockingly enough, I think this could be a nice mid-card feud to keep all four busy doing something of import for a couple of months. Intellectualism versus the personifications of pop-culture writes itself, no?
Tensai/Brodus (babyfaces) versus Primetime Playas (heel) - Just another mid-card feud I think could work quite well if they give some promo time to both sides and let them have fun with it. It could start over something completely ridiculous (Playas hitting on one of the cheerleaders?) and just explode into a in-ring feud.
Jack Swagger (heel) versus Kofi Kingston (babyface) - If the Wyatt thing is a no-no, then how about this, for the US Championship? Sell it as Swagger refocusing now that the World Championship is being held by a proper American, and Kofi is African, so...
AJ (heel) versus Kaitlyn (babyface) - They've had these two interact long enough to make a feud out of it for the diva's championship. The matches won't be that pretty, but I'd watch if only for the story behind it.