hey bro first of all you look great. that said I'm sure you want suggestions too.
arm looks great in first pose (bicep) in third pose I would try to find an angle that allows your bis to look peakier. whether rotating your arms back I don't know.
also your legs seem to be lagging in terms of definition. I would really want to see the difference between the quads and hams better. loks like it may be a matter of concentrating on flexing those muscles harder, looks like you are concentrating more on flexing your upper body.
could be the lighting, dunno.
looks like you have the calf flex down though, you can really see it.
of the 4 pics I would say the first two are pretty good. the one you need the most work on is the third one.
there are all kinds of little tips for holding certain body parts against others to make them look bigger, angles, etc.
oh yeah another thing I would do is work on giving a really stunning smile even when you are miserably dehydrated, flexing every muscle in your body as hard as you can, and tired as hell. you gotta flash those pearly whites bor!