Design in giveaway/contest apps is the second most important thing about them (first is of course the prize itself). When app has great design it is easier to enter and also provides some level of proffesionalism to promoter.
Currently, the most used giveaway apps on the market are Gleam and Rafflecopter. Gleam for me is leader – it has great simple design and functionality that offers immersive visual experience for everyone who is entering giveaway through this app.
On the other hand Rafflecopter – has even more simpler design but in this case it is dull and not interesting that much as Gleam.
The fact is Rafflecopter has been on market few more years than Gleam and still is not that good. In future, I expect Rafflecopter to totally change design of their app. Design will have to be still simple but more eyecatchy then few colors and rectangles. Gleam, has now good design, but will have to change, because design trends are always changing, so they will have to keep up to maintain their audience.