1. The patterns are up to your discretion. Obviously it would be best to use the colours from the Pokemon itself and to look to each line's design as inspiration for patterns. But really, if you are taking the time to do it, you have artistic license.
2. No. You also don't need to make eggs for Pokemon that cannot have eggs (i.e. genderless lines). Also note that each line needs an egg, and not each Pokemon.
3. You only need to make eggs for the Pokemon appearing in Topaz from those regions. (Full list of all appearing Pokemon is here.) However, I would suggest doing Topaz Pokemon first. If we can get them done, we can end this project if it becomes too much work and just use the standard egg for the canonmon.
4. The easiest would be uploading to imageshack or another file hosting website, then posting a link here. However, if you are completely opposed to that, let me know via PM when you're done and I'll give you an email to send to.

I would suggest doing one or three, then uploading those for feedback before you go ahead and do "half the eggs". Getting feedback may help you to improve and make better eggs as a whole.