Check the server you are going to.
For mounts I suggest ones that are consistently priced due to high gold vendor crafting items being needed. Sandstone drake and the JC panthers should hold their value well.
Could try moving a few TCG and other high value rare drop pets also.
Medallion of the legion can be a decent one. I've seen them as low as 4k on some servers and ul to 10k on others, so really a good bit of room to profit if you check first. Buy up 50+ of these and it really adds up. They sell quickly too. I can sell off about 60-80 a week on a high pop server.