When we review icons we are not only looking at the design and technical quality of the icons but we are also considering the potential relevance to Iconfinder users, the uniqueness of the icons, how the set fits with the rest of the content, and the potential appeal to our users. We are interested in relevance, quality, uniqueness, and variety.
Iconfinder will accept 1 variation of icon sets in each major icon style. By "major icon design style" includes glyph (solid), line, flat, 3D, skeuomorphic, cartoon, hand-drawn, and pixel. Let's say you have an icon set of "tools" (hammer, wrench, drill, compass, and pencil with ruler). You can draw each of the icons in each of those styles and submit them without any problems. So you could submit seven versions of each object (1 hammer in glyph, 1 hammer in line, 1 hammer in flat, 1 hammer in flat, ect).
We will not accept icon sets that use the exact same designs from above and simply place them on top of or inside of a colored or outline shape (circle, square, hexagon, etc). Please note, you CAN submit icons on top of or inside of a shape, but that will be considered your one variation so you cannot then submit the same icon without the shape. Our suggestion is do not submit icons on or in a shape unless the shape is integral to the design.
Please note, you DO NOT have to limit yourself to just these four styles. You are free to do hand-drawn, cartoon, 3D, and/or skeuomorphic. This rule is to cut down on the number of nearly identical icons such as doing a line icon then putting the exact same icon in a circle, a square, and a hexagon, then doing different colors of each shape. These variations do not qualify as different icons, just a minor decorative change.
However, if you want to do an icon of say, a power drill, and do a glyph version, a plain line version (no color), a color-filled line version, and a flat version that would be 100% okay. But taking that same drill in a single style, such as line, and doing a green line version, a black line version, a blue line version, then putting the same line icon on a black circle, a green circle, and a blue circle is not ok.
Allowing designers to submit unlimited variations of the same icons in this manner clogs up the search results with only the work of a single designer and limits the amount of variety a customer sees.