I’m not sure if those Tumblr URLs are just an incrementing ID (so each new post is +1 greater than the last one), or if it’s a randomly-generated string of numbers.
If you just want yours to be the entry ID, all you’d have to do is go into your section’s settings, and set the following:
- Do entries in this section have their own URLs? [check]
- Entry URL Format:
post/{id}
If you want it to be random, that’s a little more difficult. You would need to create a custom text field that stores the random number, attach it to your section, and start entering random numbers into it when creating new entries (or you could write a custom field type that handles this for you). Then your Entry URL Format would get set to post/{customFieldHandle}
instead of post/{id}
.
As for the image URL, if you have an Assets field that’s responsible for storing the entry’s main image, you can set it to restrict uploads to a single directory, and give it a subfolder based on the entry’s ID/random number custom field handle. (See http://buildwithcraft.com/docs/assets-fields#restricting-uploads-to-a-single-folder)