Darko, well i think you are new with sigs, aren't you ? Forgive me but I do not like them, but graphics stuff is all about practice. I guess you'll be making very nice sigs..
P.S. You may use 300-350 width and 100-160 height for a standar sig.
Your sigs are really good, and they do represent some work. But to be honest with you, I would say that the first sig is the most popular one I have seen. It has been taken out of the Prince of Persia Warrior Within poster. In the area I live, a lot of graphic designers have used up that idea. That is the reason why I would recommend you not to use the Prince of Persia, and maybe use another character from another game. I also think that you are new with sig making, so I would recommend you use some blur effect and different range of colours. Most of your sigs are pretty clear and they are just too solid, so I would recommend you use some filters and brushes to make them look interesting. I hope this helps.
The first one is really good but third one is cool too hehe. Name-Your-Poison.... Well after you die you won't care about what name is that poison anyway lol. Okay I'll stop hehe. You did a great job darko.
