Some notes about those creative elements:
Arguably the most impactful differentiator for your creative is color. Most brands will have a predetermined set of colors that they regularly use in their marketing materials. Try emphasizing a different brand color in each variation of your creative.
The other important aesthetic element to experiment with is the layout of your ad. Try to mix up the layout of each variation to diversify the appearance of your ad.
Of course, the main goal of your campaign is to deliver a message to your potential customers. Different phrases and word choice will resonate with different users. Try tweaking your text, substituting language to appeal to different types of audience members.
Each AdFreeway requires each campaign variation in four sizes:
300x250, 320x50, 728x90, 300x600
(Note that the AdFreeway voting overlay has a fixed 40px height that spans the width of the ad.)
You can also submit any of the following sizes in addition to those noted above:
336x280, 250x250, 300x300, 320x100, 200x200