This is a fun shot for the challenge. I like the combination of both thumbtacks and pushpins. (Or whatever you call the different styles.)
The colors are vibrant and true and the shiny quality of the steel tacks adds some dimension to what might be monotonous. There is a slight color cast of green to the shot on my monitor (another commenter noted this, too) that makes it feel like office lighting was used - though that doesn't really bother me since that is one of their habitats.
I like that you chose to leave some foreground instead of a consistent field of tacks.
I am a sucker for macros. But I think your depth of field should have been shorter, with the focus on the red tack. And maybe with more of the rule of 3s. For what it's worth. :)
This photo has such a strong greenish tint that I almost cannot view it. The 'naturalistic' take on tacks is refreshing. I like the depth of field. I find the photo a little cluttered.