So, I'm adding to your gallery but not to the challenge. Just take this as a learning experience, k :)
In the future when you make an edit or a revision you don't need to delete the page and re-submit it as new. Just hit the 'edit details' (pencil icon) link under the art ^ up there. Then upload new version and hit submit at bottom of page.
The eyes on your image is transparent because they were the same color as the background when you made the pic transparent. In the future use the green or pink I used in the edit pic so you know what will be transparent (or any color not used in the art).
Please look at the image edit I made below:
The right shows a general idea of you bird in iso perspective using an iso grid.
Edited the saddle a bit because it was just sitting there straight down....did this fix it a little? UH i need help with this ):
you really can't just eye an isometric perspective. if you're working with organic shapes rather than geometric forms, you have to lay down some isometric lines to ensure the features line up correctly. it's definitely skewed- neither head on or profile view- but it still isn't really isometric so much as faux-isometric.
The tail looks a little off in the perspective.. That might just be me.
So, i've reached the best of my abilities....i tried making wheels and i failed miserably...hopefully this now makes it more vehicle-y....
And jalonso...srsly?...that is isometric in my eyes x.x I think i've worked on this so much i really think i should just quit on this challenge.
I think you could make it more vehicle-ish (if needed for the challange) by changing his feet to tractor wheels, I mean keep the legs but have wheels for feet. Might look wierd but for some reason it sounds cool.
I give you that. It may be a vehicle and I said I'd leave for other Mod and community input regarding that aspect. Art is indeed subjective, these things happen.
I did not express myself clearly, I guess. Its not iso (in the 2:1 traditional way) was my main point and the reason I question allowing this piece in the challenge MORE SO than the bird-itude.
I dont mean to argue or anything...but a vehicle is "any means in or by which someone travels or something is carried or conveyed; a means of conveyance or transport." I don't see how a raft is more of a vehicle than a big metallic bird that you can ride and control as well.
If making it look less of a bird would fix things i will try and to that.
Any piece will say "PIXEL ART AWAITING APPROVAL!" while its waiting for it to be... ummmmmm...approved 
This is waiting because the staff will surely have issues with it. My personal opinion is that its not a 'vehicle' its a bird with armor. Additionally to that, its not quite isometric in the 2:1 sense. The angle seems iso-ish but its not to me so I have a hard time adding it to the challenge.
This has nothing to do with adding to your gallery. Its nice and I like it, I just don't see it following this week's rule. So it will sit in the public queue for other Mod input and member voting...but I strongly feel it doesn't follow the rules...k?
*You can always check to see what pieces are lingering in the queue and vote on them by hitting the first drop-down menu up there under the PJ logo, last link.
It's not "revision needed before approval" witch just means that your piece broke one of the rules, so you can't see it, it's "awaiting approval" where it's in line to get in to the gallery, and where it gets judged on weather or not it breaks the rules.
Ah thnx (: but how can you see it? It says that it hasn't been approved yet on my screen D:
I'd say "yes" to this! If it makes it, it get's my vote.
Congrats for the hard work you put in this. Textures and shading are just great.
Don't let yourself be discouraged by the challenge fail, the main point for uploading stuff is to improve (which you do).
Since it's not in the challenge anyway, I'd suggest reverting to feet.
Also the white bolts could look better, probably by making them 2-pixel wide (one light, one dark).