Quick question: have you asked spreadshirt directly what the problem with the image is and how you can correct it?
Can you post a smaller version exported as a JPG so others don't have to download an eps file (they can view the JPG inline in the post without having to have the software)?
Looking at the image, I can understand why it wasn't accepted as a flex or flock printable design. However, they do offer digital printing with a
DTG printer and I'm sure that graphic would work fine on light color shirts and dark color shirts using the
DTG process.
To understand why it was rejected , it helps to understand the method they use for their flex and flock decoration process.
Flex and flock are solid pieces of material that are cut to the shape of your image.
Imagine taking scissors and cutting all the little lines and star bursts in your image out of construction paper and then pasting them to a solid white piece of paper.
Of course they aren't cutting them with scissors and they aren't using construction paper, but just as with scissors, the more complex the image is, and the more colors it has, the more time it will take to put all those pieces together, line them up, and properly apply it to the t-shirt.
I think it might be easier to realize that the flex and flock t-shirt decoration methods at spreadshirt aren't "printed". They are solid color pieces of high quality material specially made for t-shirts that are cut using a machine that cuts your design out of a solid sheet of material. That cut material is then applied to the t-shirt.
Before I learned more about this process, it took me a while to get my head around it. But once you see a few videos of vinyl/flock t-shirt material being cut and applied, it starts to make more sense
This video will show you the machine that does the cutting and the overall process:
YouTube - Heat Press Transfer Vinyl Tutorial
This video will show you the "weeding" process that has to be done by hand for each of the "whitespace" areas in between the design:
YouTube - Heat Applied Vinyl for T-Shirts
This video from spreadshirt also briefly shows the process:
YouTube - Spreadshirt - Hands per piece, how your t-shirt is made
So in between all the star bursts, someone would have to weed and pull away the excess vinyl material to get it to look as you have it designed. That weeding is time (labor) that has to be paid for, so the more complex it is, the more they have to charge as a base price, which means the more that you would need to charge your end customers. At a certain point of design complexity, it doesn't become economically viable for them or you to produce a t-shirt in that method.
When you add a second color, it makes it even more complicated, as those two colors need to be carefully lined up to look just right.
Hope this helps some
I think your design, without the star "rays", with the simple yellow outline and the yellow icon image int he middle
might work. But even then, it's going to be more complicated than if it was just the red star and the icon image in the middle was just the garment color.
I think if you talk to spreadshirt, they may be able to give you tips and first hand knowledge as to why the image wasn't accepted and maybe what you could do to make it better fit that t-shirt decoration method.
Or you could just choose the
DTG method and upload a transparent PNG version of your design
'Will it work?' thread for Vector Submission 
