(1) I want to redirect...

http://www.mywebsite.com/johndoe/picture123.jpg

to

http://www.mywebsite.com/johndoe/latestpicture.jpg

How do I do this?

(2) How do I do the above, but if I want to redirect...

http://www.mywebsite.com/johndoe/picture_12366.jpg
http://www.mywebsite.com/johndoe/picture_152566.jpg
http://www.mywebsite.com/johndoe/picture_12312.jpg
http://www.mywebsite.com/johndoe/picture_125235.jpg
http://www.mywebsite.com/johndoe/picture_23366.jpg
http://www.mywebsite.com/johndoe/picture_36346.jpg
(basically anything picture_*.jpg)

to

http://www.mywebsite.com/johndoe/latestpicture.jpg

rewrite ^/johndoe/picture_\d+.jpg /johndoe/latestpicture.jpg last;

rewrite ^/johndoe/picture_\d+\.jpg /johndoe/latestpicture.jpg last;