The Americans impressed Brown in a 2-1 friendly reserve win over Celtic on Tuesday. Midfielder Peterlin, 22, is nearing the end of a one-year deal at Goodison Park and has yet to play for the first team. Striker Arnoux, 21, also joined Everton last summer.
"They are good players and they are here for another practice match next week," said Brown.
"If they maintain the promise that we've seen, they must be candidates for signing offers. I'm not getting complacent about that, obviously we may have to compete to get them.
"But we're looking at them with considerable interest and it just proves to the fans of Motherwell that we're not letting the grass grow under our feet.
"In the event of perhaps the two loan players going back to Everton, we have started early looking at possible replacements.
"We might have to do a bit of negotiating to get them either on loan or there might be a transfer fee.
"I haven't discussed it at that level with (Everton manager) David Moyes, who's a pal of mine and has kindly given us a look at the players."