My suggestions will basically consist in minor "cosmetic" changes, neither I believe they're updates to be kept in priority, but they would be nice to be kept in mind.
1) Relocate thieving stalls and training into the OSRS Ardougne teleport. In my opinion it would be nice because there are actual stalls there. Could make some use of East/West Ardougne area. Combined with the function of the deep wilderness lever next to the Ardougne castle. Credits to "I just rag" with the lever idea: (http://spawnpk.net/forums/showthread.php?t=2783)
2) Make the mining training spot more realistic and take it into some sort of Falador telport inside the mining guild. At the moment it's inside the Monkey Madness quest area with a banker next to you, making it easy. This change would indirectly make it a bit more stressfull to 99 it since you would have to bank your ores somewhere without having a banker near you, with the obvious intention of making it a bit more harder skill, similar to the difficulty of Herblore or Agility.
3) Catherby would be a nice location to give some life to. Convenient place to train fishing and cooking. Also decent fishing spots without a handy bank near you. (Few steps, but not near).
4) Take the Slayer spawning area towards the Slayer tower near Canifis, distributing NPC's into the different floors and rooms. The spawning room sometimes gets crowded.
Thanks