standardize pictures of locations for all relevant menupages

[kir12]

we would like to add location pictures to the remaining menupages that detail events:

• the guests page should have a picture of the assembly hall
• artists alley needs a picture of ken miller (current plaza picture may be incorrect)
  • see if vendors is getting a different location, if so add it
• the cosplay page should have location pictures for both the assembly hall and pine wind garden due to cosplay contest
• inside the convention maps page, add pictures of all the relevant convention locations

[kir12]

closed by #27