That's actually pretty good, but here are somethings you need done.
1. It needs to be transparent. Remove all the grey of the shirt so that the player can color it however they want. (maybe even remove ALL the grey and just use tinted transparent regions where you want it to be darker)
2. Do not post things like "Is this good enough to release?" in any of the Files sections (addons, maps, music or decals). Instead ask a friend that can give you an honest opinion or just look at it yourself. If you feel it compares with the other decals then release it, if you are not proud of it and feel as if it isn't very good, don't release it. The files sections are for finished mods only.
3. This isn't necessarily required but it is nice. When dealing with skin, it is always good to make 2 versions. One Pale skin version and One yellow skin version. If you do not want to make more than one then it is always better to go with yellow skin, because that is what the default decals use. If you do choose to use Yellow you should be sure to use the same yellow that defaults use. You can find an example in Blockland/Add-Ons/Decals_defaults.zip The medieval tunic decal has a skin color that you can do the eyedropper tool on or something.
If you follow some of those tips and keep doing this I can see you becoming a very good decal maker in the future