pam..it's all your art work..not the modeller's own... you made the change. your final product.. (nice pix..though a bit sad..i want to hug rudolf and smooch his nose..)

see..that made the difference..that' s your own art work.

sans anything that you had done to it.. let; s say you bought the model.. and just put it up and say that's mine.. nah..that's not right. as long as you tweaked it a bit..put in your own stuff..no matter even if it was a single cell on a poser  figure.it's yours.

the person who modelled the mountains but it up for sale.. he/she knew someone was gonna take it..and put it in their work.. they gave up the rights to it when you bought it. you have every right to use it  how you want t your art work.. barring reselling the model as a model itself... and saying you did it..

hope that helps... cheers..

will email you later down the week.. :-)