You can simply add UIImageView with your picture as cell's subview. It will work both ways --with and without creating a custom cell.
Here's some sample code:
- (UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath
{
NSString *kCellID = [NSString stringWithFormat:@"%d", indexPath.row];
UITableViewCell *cell = [tableView dequeueReusableCellWithIdentifier:kCellID];
cell = [[[UITableViewCell alloc] initWithStyle:UITableViewCellStyleDefault reuseIdentifier:kCellID] autorelease];
UIImageView *MyImageView = [[UIImageView alloc] initWithFrame:CGRectMake(100.0, 33.0, 300.0, 110.0)]; //put your size and coordinates here
MyImageView.image = [UIImage imageNamed:@"MyImage.png"];
[cell.contentView addSubview: MyImageView];
[MyImageView release];
return cell;
}