One interesting sort of thing I kind of realized thinking on this some more is that for the most part Peter Parker seems to always have worn the black suit more or less as a costume as opposed to a symbiote that enters into his body like it does with Brock. I suppose this is due to the comic writer's not conceiving of the black suit as a symbiote type creature for quite sometime after it was originally introduced (fanplanation I suppose could try and rationalize it didn't like Peter's irradiated blood but I don't recall ever seeing this mentioned)...
With that being said I have to get this idea out of my system:
This whole thing with the symbiote being presented only as a costume for a while in the comics, makes me think this oddity from the comics is something any film featuring Venom could really try and run with. The suit assuming a more tar like texture and scaled down appearance I suppose could also coincide with Eddie not wearing the symbiote for a while. When off of him, it could attach to an article of clothing before being able to mimic it as the symbiote is then hung up in a closet as a copy of this piece of clothing while it's hibernating perhaps. Going along with this, perhaps there can be something like the costume making machine seen in Secret Wars #8
(inside Doom's fortress on Beyonder's Battleworld) but instead on the alien spaceship in the movie. This machine on the ship, could be used to store some symbiote suits for the ship's crew that are contained within the capsules
(as seen on the trailer) that keep the symbiotes in a stassis like state that the ships crew could open similar to accessing an article of clothing in a closet.
The absence from having the suit on all the time would create a bit of tension in the relationship between the host and symbiote with the host essentially going through withdrawal if away for too long. In the comics it's interesting how Eddie can switch from being totally ok with killing someone to a 180 degree change in direction not wanting to all of a sudden. Past precedent doesn't seem to dictate future behavior all the time and I think sort of a who is in control the symbiote or the host question could really be played with by keeping them apart at times. Of course once the symbiote attaches to host it could assume either a
costumed puppet like look (wearing it like a costume)or full on monstrous hulk like expansion (if goes back within the host's body and resides for a while).
http://forums.superherohype.com/showthread.php?t=541385&page=39