Yohan kindly requested some early Christian art expressive of the eary church’s commitment to fellowship. I have had some difficulty in finding anything expressly on that subject.
I note the statement of the early Church leader, Tertullian: “See how these Christians love one another.” If we look to the example of Christ which inspired such rich fellowship, there is significant art on such related subjects that would lend itself to the Christian fellowship that abounded in the early church.
I will begin by introducing some of the earliest Christian art that we have, that of the catacombs in Rome. For background to that art, one of the most direct and helpful sites I have found is http://www.sacred-destinations.com/italy/rome-catacombs. The immediately following information and photographs come from that site.
The Roman catacombs were a maze of underground tunnels and coves on the outskirts of Rome where Christians burried their dead on small shelves dug into the dirt lining the tunnels. In times of severe persecution the Christians also worshiped there. For these purposes the Christians came to adorn the catacombs with art intended to reflect their values in worship. There were certain themes and symbols common to that art. One of those was the symbol of the fish, representing the Christ:
Another very common theme was the depiction of Jesus as the Good Shepherd:
See http://www.scrollpublishing.com/store/catacomb-pictures.html for the origin of the following catacomb artistic reference to the Christ as the Good Shepherd:
Certainly, the depiction of the Good Shepherd would help His flock to feel safe under His care, freeing them for fellowship with each other and with Him.
For photographs of immediately post-Constantine art in the Church at Rome, see http://smarthistory.khanacademy.org/santa-pudenziana-rome.
We don’t have artistic representations of the gatherings of the early Christians or of how they “loved one another.” But we do have artistic interpretations of Jesus’ compassion for all who sought his fellowship or aid, his love of the company of women – even of the disreputable, of children, of men -even of sinners.
Relating in part back to the early church prior to Constantine but constructed perhaps as late as the Ninth Century is the Basilica of Santa Prassede in Rome. For an excellent video discussion of the art in that church see http://smarthistory.khanacademy.org/santa-prassede, and for an excdellent photographic presentation of its art see http://www.arttrav.com/rome/santa-prassede-mosaics/. For a video discussion of the architecture of the early Roman church, Santa Sabina, see http://smarthistory.khanacademy.org/santa-sabina, for photographic representations of its interior art, see http://www.sacred-destinations.com/italy/rome-santa-sabina and of the art on its carved wooden door, see http://www.sacred-destinations.com/italy/rome-santa-sabina-door.htm. I note that upon legalization of the Christian Church by Constantine, the Church took no time to adopt and transform Roman architectural and visual arts to serve its purposes. The size of the basillicas also suggests to me, compared to prior Christian art and architecture (the catacombs) a dramatic mushrooming of the Church’s membership and patronage lended to it.
For the architecture of another church of that same era, Santa Maria Maggiore, see http://smarthistory.khanacademy.org/santa-maria-maggiore.
Yohan, I hope this is some help to you, but my suspicion is that you will want to look at some modern Christian art which may be less representational and more allegorical or expressive of fellowship. For any modern art, I, and likely you, will be more restricted by copyright law. Here are some sites of Christian art that might help you: http://www.christianlink.com/art/ or http://christian-artists.us/2.html. Or, you might search for art of your favorite artist or particular themes or passages at http://www.biblical-art.com/artist.asp. or http://www.artbible.info/bible/new-testament.html.
I suspect you may find something of simple design that is also symbolic of the fellowship that your church enjoys or envisions. Perhaps some visitor to the site will have some ideas for you. I would be interested to know what is your solution.
Links to my site:
Home Page https://bibleartists.wordpress.com/